251
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Zehn D, Bevan MJ. T cells with low avidity for a tissue-restricted antigen routinely evade central and peripheral tolerance and cause autoimmunity. Immunity 2006; 25:261-70. [PMID: 16879996 PMCID: PMC2774714 DOI: 10.1016/j.immuni.2006.06.009] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Revised: 06/12/2006] [Accepted: 06/15/2006] [Indexed: 10/24/2022]
Abstract
T cells causing autoimmunity must escape tolerance. We observed that CD8(+) T cells with high avidity for an antigen expressed in the pancreas, kidney, and thymic medulla were efficiently removed from a polyclonal repertoire by central and peripheral tolerance mechanisms. However, both mechanisms spared low-avidity T cells from elimination. Neither the introduction of activated, self-antigen-specific CD4(+) helper T cells nor a global inflammatory stimulus were sufficient to activate the low-avidity CD8(+) T cells and did not break tolerance. In contrast, challenge with a recombinant bacterium expressing the self antigen primed the low-avidity T cells, and the animals rapidly developed autoimmune diabetes. We suggest that whereas thymic and peripheral tolerance mechanisms remove cells that can be primed by endogenous amounts of self antigen, they do not guard against tissue destruction by low-avidity effector T cells, which have been primed by higher amounts of self antigen or by crossreactive antigens.
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Affiliation(s)
- Dietmar Zehn
- Department of Immunology, Howard Hughes Medical Institute, University of Washington Seattle, Washington 98195
| | - Michael J. Bevan
- Department of Immunology, Howard Hughes Medical Institute, University of Washington Seattle, Washington 98195
- Correspondence:
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252
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Wuensch SA, Pierce RH, Crispe IN. Local Intrahepatic CD8+T Cell Activation by a Non-Self- Antigen Results in Full Functional Differentiation. THE JOURNAL OF IMMUNOLOGY 2006; 177:1689-97. [PMID: 16849478 DOI: 10.4049/jimmunol.177.3.1689] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The response of T cells to liver Ags sometimes results in immune tolerance. This has been proposed to result from local, intrahepatic priming, while the expression of the same Ag in liver-draining lymph nodes is believed to result in effective immunity. We tested this model, using an exogenous model Ag expressed only in hepatocytes, due to infection with an adeno-associated virus vector. T cell activation was exclusively intrahepatic, yet in contrast to the predictions of the current model, this resulted in clonal expansion, IFN-gamma synthesis, and cytotoxic effector function. Local activation of naive CD8(+) T cells can therefore cause full CD8(+) T cell activation, and hepatocellular presentation cannot be used to explain the failure of CTL effector function against some liver pathogens such as hepatitis C.
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Affiliation(s)
- Sherry A Wuensch
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA.
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253
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Abstract
Recent elucidation of the role of central tolerance in preventing organ-specific autoimmunity has changed our concepts of self/nonself discrimination. This paradigmatic shift is largely attributable to the discovery of promiscuous expression of tissue-restricted self-antigens (TRAs) by medullary thymic epithelial cells (mTECs). TRA expression in mTECs mirrors virtually all tissues of the body, irrespective of developmental or spatio-temporal expression patterns. This review summarizes current knowledge on the cellular and molecular regulation of TRA expression in mTECs, outlines relevant mechanisms of antigen presentation and modes of tolerance induction, and discusses implications for the pathogenesis of autoimmune diseases and other biological processes such as fertility, pregnancy, puberty, and tumor defense.
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Affiliation(s)
- Bruno Kyewski
- Division of Developmental Immunology, Tumor Immunology Program, German Cancer Research Center, 69120 Heidelberg, Germany.
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254
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Abstract
Caspases are responsible for crucial aspects of inflammation and immune-cell death that are disrupted in a number of genetic autoimmune and autoinflammatory diseases. The caspase family of proteases can be divided into pro-apoptotic and pro-inflammatory members based on their substrate specificity and participation in separate signalling cascades. However, as discussed here, evidence has emerged over the past few years that a number of the caspases thought to be involved solely in apoptosis also contribute to specific aspects of immune-cell development, activation and differentiation, and can even protect cells from some forms of cell death.
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Affiliation(s)
- Richard M Siegel
- Immunoregulation Unit, Autoimmunity Branch, NIAMS, National Institutes of Health, Building 10 Room 9N238, Bethesda, Maryland 20892, USA.
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255
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Uldrich AP, Berzins SP, Malin MA, Bouillet P, Strasser A, Smyth MJ, Boyd RL, Godfrey DI. Antigen challenge inhibits thymic emigration. THE JOURNAL OF IMMUNOLOGY 2006; 176:4553-61. [PMID: 16585545 DOI: 10.4049/jimmunol.176.8.4553] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
T cell development in the thymus involves a series of TCR-mediated control points including TCR-beta selection and positive and negative selection. Approximately half of the thymic sojourn is spent in the medulla, where thymocytes undergo final maturation before emigrating to the periphery. Although it is acknowledged that thymic emigration is an active process, relatively little is known about how this is regulated, why it takes so long, and whether TCR-mediated signaling can influence this step. Using wild-type and TCR transgenic mice, we found that Ag injected i.v. or intrathymically led to a striking reduction in the number of recent thymic emigrants (RTE) in the periphery. This was caused by inhibition of T cell export rather than peripheral deletion, because a cohort of RTE that was already released before in vivo Ag challenge was not depleted, and similar results were observed in Bim-deficient mice, which have impaired T cell deletion. Within the thymus, the loss of RTE was associated with retention of medullary thymocytes rather than increased negative selection. In addition to Ag-specific inhibition of export, some TCR-independent suppression of emigration was also observed that appeared to be partly the result of the inflammatory cytokine TNF. Thus, in addition to its accepted role in intrathymic selection events, TCR signaling can also play an important role in the regulation of thymic emigration.
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MESH Headings
- Animals
- Antigens/administration & dosage
- Cell Movement/immunology
- Enterotoxins/administration & dosage
- Enterotoxins/immunology
- Injections, Intralymphatic
- Injections, Intravenous
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
- Signal Transduction
- Superantigens/administration & dosage
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- T-Lymphocytes/physiology
- Thymus Gland/cytology
- Thymus Gland/immunology
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Affiliation(s)
- Adam P Uldrich
- Department of Microbiology and Immunology, University of Melbourne, Parkville, Victoria, Australia.
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256
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Brown N, Nagarkatti M, Nagarkatti PS. Induction of apoptosis in murine fetal thymocytes following perinatal exposure to diethylstilbestrol. Int J Toxicol 2006; 25:9-15. [PMID: 16510352 DOI: 10.1080/10915810500488353] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Perinatal exposure to diethylstilbestrol (DES) is known to cause thymic atrophy in mice, although the precise mechanism remains unclear. In the current study the authors investigated whether perinatal exposure to DES would trigger apoptosis in thymocytes. To this end, C57BL/6 pregnant mice were injected intraperitoneally (i.p.) on gestational day (gd)-15 and -16 with 5 microg/kg DES. Analysis of thymi harvested from mice on gd-17, gd-19 and postnatal day (PD)-1, showed a significant reduction in thymic cellularity on gd-17 only. Additionally, DES treatment significantly altered the proportion and absolute number of T-cell subsets, particularly on gd-17. Apoptosis was increased in DES-treated thymocytes when compared to the controls and was seen only on gd-17. Moreover, DES-treated gd-17 thymocytes had increased Asp-Glu-Val-Asp (DEVDase) activity. Microarray analysis of 96 apoptotic genes in gd-17 thymocytes revealed that exposure to DES increased the expression of several apoptotic genes primarily belonging to tumor necrosis factor (TNF) and TNF receptor (TNFR) family. Taken together, these results suggest that DES-induced thymic atrophy following perinatal exposure may result, at least in part, from increased apoptosis mediated by death receptor pathway involving TNF family members.
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Affiliation(s)
- Nicole Brown
- Department of Microbiology and Immunology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298-0613, USA
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257
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Hoyne GF, Goodnow CC. The use of genomewide ENU mutagenesis screens to unravel complex mammalian traits: identifying genes that regulate organ-specific and systemic autoimmunity. Immunol Rev 2006; 210:27-39. [PMID: 16623762 DOI: 10.1111/j.0105-2896.2006.00363.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
T-cell development is perhaps one of the best understood processes of mammalian cell differentiation, as many of the genes and pathways have been identified. By contrast, relatively little is known about the genes and pathways involved in immunological tolerance to self-antigens. Here, we describe the challenges associated with a genomewide screen designed at identifying new immune regulatory genes that uses a model of organ-specific autoimmunity leading to type 1 diabetes. The successful propagation and identification of the new gene variants will shed light on the various developmental checkpoints in lymphocyte development that are crucial for establishing tolerance to self-antigens.
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Affiliation(s)
- Gerard F Hoyne
- Australian Cancer Research Foundation Genetics Laboratory and Australian Phenomics Facility, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia.
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258
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Sigal LH. Basic science for the clinician 37: Protecting against autoimmunity-tolerance: mechanisms of negative selection in the thymus. J Clin Rheumatol 2006; 12:99-101. [PMID: 16601548 DOI: 10.1097/01.rhu.0000208636.30695.75] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
As noted in previous articles in this series, tolerance, the ability of the immune system to differentiate self from nonself and leave the former alone, is a vital characteristic of a successful (and safe) immune system. With the detection of the molecule called aire (autoimmune regulator), the mechanism whereby autoreactive thymocytes encounter extrathymic proteins within the thymus and therefore are deleted, is now far better understood; aire was the subject of a prior article in this series. The absence of aire leads to autoimmune polyendocrinopathy, proof that aire is the center of an amazing "filtering" system. However, there are other mechanisms at work. Irregularities in expression of other proteins such as hypoxia-induced factor-1 (HIF-1) and CTLA4, have been implicated in autoimmune disease, the former in rheumatoid arthritis, the latter in autoimmune thyroid disease and lupus. Defects in intracellular factors involved in transcription of key apoptotic proteins have also been implicated in the escape of autoreactive thymocytes from the thymus, leading to autoimmune and lymphoproliferative syndromes as well. Changes in the proteins that oversee acetylation of histone lead to differential patterns of gene expression. At least 2 proteins involved in this process, HDAC and nur77, have been implicated in changes in survival of thymocytes. Yet again, there are multiple layers at work in the immune system; I have no idea how many more will be brought to light, which are phylogenetically most ancient or which will prove the most clinically relevant. For now, it is enough to bask in our new-found knowledge and know that the time from laboratory oddity, to animal model development, to therapeutic and/or diagnostic applications grows shorter each year since the molecular biologic revolution.
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Affiliation(s)
- Leonard H Sigal
- Pharmaceutical Research Institute, Bristol-Myers Squibb, J.3100, PO Box 4000, Princeton, NJ 08543-4000, USA.
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259
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Nitta T, Nasreen M, Seike T, Goji A, Ohigashi I, Miyazaki T, Ohta T, Kanno M, Takahama Y. IAN family critically regulates survival and development of T lymphocytes. PLoS Biol 2006; 4:e103. [PMID: 16509771 PMCID: PMC1393758 DOI: 10.1371/journal.pbio.0040103] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Accepted: 12/27/2005] [Indexed: 11/19/2022] Open
Abstract
The IAN (immune-associated nucleotide-binding protein) family is a family of functionally uncharacterized GTP-binding proteins expressed in vertebrate immune cells and in plant cells during antibacterial responses. Here we show that all eight IAN family genes encoded in a single cluster of mouse genome are predominantly expressed in lymphocytes, and that the expression of IAN1, IAN4, and IAN5 is significantly elevated upon thymic selection of T lymphocytes. Gain-of-function experiments show that the premature overexpression of IAN1 kills immature thymocytes, whereas short hairpin RNA-mediated loss-of-function studies show that IAN4 supports positive selection. The knockdown of IAN5 perturbs the optimal generation of CD4/CD8 double-positive thymocytes and reduces the survival of mature T lymphocytes. We also show evidence suggesting that IAN4 and IAN5 are associated with anti-apoptotic proteins Bcl-2 and Bcl-xL, whereas IAN1 is associated with pro-apoptotic Bax. Thus, the IAN family is a novel family of T cell-receptor-responsive proteins that critically regulate thymic development and survival of T lymphocytes and that potentially exert regulatory functions through the association with Bcl-2 family proteins.
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Affiliation(s)
- Takeshi Nitta
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Mariam Nasreen
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Takafumi Seike
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Atsushi Goji
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Izumi Ohigashi
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Tadaaki Miyazaki
- 2Division of Molecular Immunology, Institute for Genetic Medicine, Hokkaido University, Sapporo, Japan
| | - Tsutomu Ohta
- 3Medical Genomics Center, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan
| | - Masamoto Kanno
- 4Department of Immunology, Graduate School of Biomedical Sciences, Hiroshima University, Minami-ku, Hiroshima, Japan
| | - Yousuke Takahama
- 1Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
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260
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Eleftheriadis T, Voyatzi S, Antoniadi G, Kartsios C, Liakopoulos V, Paraskevopoulos P, Galaktidou G. Major histocompatibility complex class I restricted T-cell autoreactivity in human peripheral blood mononuclear cells. Cell Immunol 2006; 240:62-7. [PMID: 16884707 DOI: 10.1016/j.cellimm.2006.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2006] [Revised: 06/16/2006] [Accepted: 06/20/2006] [Indexed: 11/29/2022]
Abstract
During selection in the thymus or any subsequent response, T-cells recognize peptides bound to major histocompatibility complex (MHC) molecules. Peptides produced by lysosomes or by proteasome/immunoproteasome stimulate CD4+ or CD8+ T-cell, respectively. Inflammation alters components of both antigen-processing pathways resulting in the production of different peptides. The role of such changes in self/non-self discrimination was examined in autologous mixed peripheral blood mononuclear cell cultures. Stimulator cells were incubated in the presence or absence of INF-gamma, with or without lysosome inhibitors (ammonium chloride/chloroquine), cathepsin inhibitor (E-64), or proteasome/immunoproteasome inhibitor (epoxomicin). Responder cells were added and zeta-chain phosphorylated forms were used as read out. INF-gamma did not affect zeta-chain phosphorylated forms, which means that the expected INF-gamma induced alterations in antigen processing machinery do not influence self/non-self discrimination. Surprisingly, the completely phosphorylated 23-kDa zeta-chain was always present except in the case of epoxomicin, indicating the presence of MHC class I restricted autoreactive CD8+ T-cells but not of MHC class II restricted autoreactive CD4+ T-cells, possibly due to more efficient negative selection in the thymus of the latter. Autoimmunity is prevented due to absence of help by CD4+ T-cells. This conclusion was confirmed by the lack of differences in IL-2 levels in cell culture supernatants, as well as, by the absence of differences in cell proliferation under the various conditions described above.
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261
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Kurobe H, Liu C, Ueno T, Saito F, Ohigashi I, Seach N, Arakaki R, Hayashi Y, Kitagawa T, Lipp M, Boyd RL, Takahama Y. CCR7-Dependent Cortex-to-Medulla Migration of Positively Selected Thymocytes Is Essential for Establishing Central Tolerance. Immunity 2006; 24:165-77. [PMID: 16473829 DOI: 10.1016/j.immuni.2005.12.011] [Citation(s) in RCA: 213] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 10/31/2005] [Accepted: 12/27/2005] [Indexed: 01/05/2023]
Abstract
Immature CD4+CD8+ thymocytes, which are generated in the thymic cortex, are induced upon positive selection to differentiate into mature T lymphocytes and relocate to the thymic medulla. It was recently shown that a chemokine signal via CCR7 is essential for the cortex-to-medulla migration of positively selected thymocytes in the thymus. However, the role of the cortex-to-medulla migration in T cell development and selection has remained unclear. The present study shows that the developmental kinetics and the thymic export of mature thymocytes were undisturbed in adult mice lacking CCR7 or its ligands (CCR7L). The inhibition of sphingosine-1-phosphate-mediated lymphocyte egress from the thymus led to the accumulation of mature thymocytes in the cortex of CCR7- or CCR7L-deficient mice, unlike the accumulation in the medulla of normal mice, thereby suggesting that mature thymocytes may be exported directly from the cortex in the absence of CCR7 signals. However, the thymocytes that were generated in the absence of CCR7 or CCR7L were potent in causing autoimmune dacryoadenitis and sialadenitis in mice and were thus incapable of establishing central tolerance to organ-specific antigens. These results indicate that CCR7-mediated cortex-to-medulla migration of thymocytes is essential for establishing central tolerance rather than for supporting the maturation or export of thymocytes.
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Affiliation(s)
- Hirotsugu Kurobe
- Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima 770-8503, Japan
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262
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Sigal LH. Basic science for the clinician 36: protecting against autoimmunity: tolerance and aire, the immunologic shadow, and other mechanisms of negative selection in the thymus. J Clin Rheumatol 2006; 12:44-6. [PMID: 16484883 DOI: 10.1097/01.rhu.0000200338.09858.16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
One of the miracles of immunology is tolerance, the ability of the immune system to differentiate self from nonself and leave the former alone. Autoreactive thymocytes (the cells that would otherwise differentiate into mature autoaggressive T cells) are deleted from the emerging immunologic repertoire within the thymus; only a very small proportion of thymocytes survive the thymus--perhaps 2% to 5% emerge to become mature T cells in the periphery, the rest dying to assure tolerance. This apparent wastage somehow works to the benefit of the developing animal and if the process works, all goes well for the maturing immune system. In some autoimmune syndromes, autoreactive thymocytes are not eliminated within the thymus by either clonal deletion or activation-induced cell death; these then emerge to wreak their havoc. However, how does this deletion happen? Recent research from a number of groups has (incredibly!) identified expression of nonthymic, nonlymphoid proteins within the thymus (casting of the "immunologic shadow of self"), and this is under the control of a single protein: AIRE (autoimmune regulator). By allowing autoreactive thymocytes to encounter a broad spectrum of proteins from extrathymic organs, aire allows deletion of these cells and the maintenance of tolerance. The absence of aire leads to autoimmune polyendocrinopathy, proof that aire is the center of an amazing "filtering" system. These and other molecular mechanisms underlying tolerance are explored in this and the next paper in this series.
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Affiliation(s)
- Leonard H Sigal
- Pharmaceutical Research Institute, Bristol-Myers Squibb, Princeton, NJ 08543-4000, USA.
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263
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Nitta T, Takahama Y. [Central tolerance and autoimmune diseases]. NIHON RINSHO MEN'EKI GAKKAI KAISHI = JAPANESE JOURNAL OF CLINICAL IMMUNOLOGY 2006; 29:8-15. [PMID: 16505598 DOI: 10.2177/jsci.29.8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Central tolerance is established by the repertoire selection of immature T lymphocytes in the thymus, avoiding autoimmune responses to self-antigens. Differential ligand-TCR interactions that result in positive and negative selection initiate differential intracellular signals that, in turn, lead to the survival-or-death decision of immature thymocytes. TCR signal dysregulation due to the mutation of ZAP-70 or defective apoptosis of autoreactive thymocytes due to the deficiency of pro-apoptotic protein Bim impair tolerance and cause autoimmunity. Thymic repertoire selection also induces the development of CD25(+)CD4(+) regulatory T cells, which play important roles for maintaining peripheral tolerance. Furthermore, the establishment of central tolerance requires the development of thymic medulla that is mediated by the activation of NF-kappaB signaling pathway, promiscuous expression of tissue-specific self-antigens by medullary epithelial cells that is regulated by AIRE, and cortex-to-medulla migration of developing thymocytes that is regulated by CCR7-mediated chemokine signals.
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Affiliation(s)
- Takeshi Nitta
- Division of Experimental Immunology, Institute for Genome Research, University of Tokushima
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264
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Thien C, Langdon W. c-Cbl and Cbl-b ubiquitin ligases: substrate diversity and the negative regulation of signalling responses. Biochem J 2006; 391:153-66. [PMID: 16212556 PMCID: PMC1276912 DOI: 10.1042/bj20050892] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The activation of signalling pathways by ligand engagement with transmembrane receptors is responsible for determining many aspects of cellular function and fate. While these outcomes are initially determined by the nature of the ligand and its receptor, it is also essential that intracellular enzymes, adaptor proteins and transcription factors are correctly assembled to convey the intended response. In recent years, it has become evident that proteins that regulate the amplitude and duration of these signalling responses are also critical in determining the function and fate of cells. Of these, the Cbl family of E3 ubiquitin ligases and adaptor proteins has emerged as key negative regulators of signals from many types of cell-surface receptors. The array of receptors and downstream signalling proteins that are regulated by Cbl proteins is diverse; however, in most cases, the receptors have a common link in that they either possess a tyrosine kinase domain or they form associations with cytoplasmic PTKs (protein tyrosine kinases). Thus Cbl proteins become involved in signalling responses at a time when PTKs are first activated and therefore provide an initial line of defence to ensure that signalling responses proceed at the desired intensity and duration.
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Affiliation(s)
- Christine B. F. Thien
- School of Surgery and Pathology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Correspondence may be addressed to either author (email or )
| | - Wallace Y. Langdon
- School of Surgery and Pathology, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
- Correspondence may be addressed to either author (email or )
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265
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Carreño LJ, González PA, Kalergis AM. Modulation of T cell function by TCR/pMHC binding kinetics. Immunobiology 2006; 211:47-64. [PMID: 16446170 DOI: 10.1016/j.imbio.2005.09.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Accepted: 09/05/2005] [Indexed: 01/19/2023]
Abstract
The interaction between the T cell receptor (TCR) and the peptide-MHC complex (pMHC) at the interface between the T cell and the antigen presenting cell (APC) is the main event controlling the specificity of antigen recognition by T cells. It is thought that TCR/pMHC binding kinetics are critical for the selection of the T cell repertoire in the thymus, as well as the activation of mature T cells in the periphery. One of the binding parameters that conditions T cell activation by pMHC ligands is the half-life of the TCR/pMHC interaction. This kinetic parameter is highly significant for the regulation of T cell activation and therefore determines the capacity of T cells to respond against pathogen- and tumor-derived antigens, avoiding self-reactivity. Several studies support the notion that T cells are activated only by TCR/pMHC interactions that are above a threshold of half-life. pMHC complexes that bind TCRs with half-lives below that threshold behave as null or antagonistic ligands. However, since prolonged half-lives can also impair T cell activation, there seems to be a ceiling for the TCR/pMHC half life that leads to efficient activation of T cells. According to these observations, efficient T cell activation would require an optimal half-life of TCR/pMHC interaction. These kinetic restrictions for T cell activation are important to generate a protective adaptive immune response minimizing cross-reactivity against self-constituents. The nature of the TCR/pMHC interaction defines in the thymus whether a thymocyte develops into a mature T cell or is eliminated by apoptosis. In addition, the kinetics of TCR/pMHC binding can determine the type of response shown by mature T cells in the periphery. Although several studies have focused on the modulation of T cell function by the affinity of the TCR/pMHC interaction, the binding kinetics rules governing T cell activation remain poorly understood. Here we review recent data and propose a new model for the regulation of T cell function by TCR/pMHC binding kinetics.
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Affiliation(s)
- Leandro J Carreño
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Alameda #340, Santiago, Chile
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266
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Abstract
Immunological tolerance is a complex series of mechanisms that impair the immune system to mount responses against self antigens. Central tolerance occurs when immature lymphocytes encounter self antigens in the primary lymphoid organs, and consequently they die or become unreactive. Peripheral tolerance occurs when mature lymphocytes, escaped from negative selection during ontogeny, encounter self antigens in secondary lymphoid organs and undergo anergy, deletion or suppression. A heterogeneous family of T regulatory cells has recently been identified, which have been found to play an important role in suppressing immune responses against self. Failure or breakdown of immunological tolerance results in autoimmunity and autoimmune diseases. Such events are related to both genetic and environmental factors, the latter being mainly represented by infections. Infectious agents can indeed promote autoimmune responses either by inducing tissue inflammation and therefore an unintended bystander activation of autoreactive T cells, or by promoting T cell responses to microbial epitopes that cross react against self peptides.
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Affiliation(s)
- Sergio Romagnani
- Department of Internal Medicine, Excellence Centre Denothe, University of Florence, Florence, Italy.
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267
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Reichardt P, Gunzer M. The biophysics of T lymphocyte activation in vitro and in vivo. Results Probl Cell Differ 2006; 43:199-218. [PMID: 17068973 DOI: 10.1007/400_021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
T cell activation is crucial for the development of specific immune reactions. It requires physical contact between T cells and antigen-presenting cells (APC). Since these cells are initially located at distinct positions in the body, they have to migrate and find each other within secondary lymphoid organs. After encountering each other both cells have to maintain a close membrane contact sufficiently long to ensure successful signaling. Thus, there is the necessity to temporarily synchronize the motile behavior of these cells. Initially, it had been proposed that during antigen recognition, T cells receive a stop signal and maintain a stable contact with APC for several hours when an appropriate APC has been encountered. However, direct cell observation via time-lapse microscopy in vitro and in vivo has revealed a different picture. While long contacts can be observed, many interactions appear to be very short and sequential despite efficient signaling. Thus, two concepts addressing the biophysics of T cell activation have emerged. The single encounter model proposes that after a period of dynamic searching, a T cell stops to interact with one appropriately presenting APC until signaling is completed. The serial encounter model suggests that T cells are able to collect a series of short signals by different APC until a critical activation threshold is achieved. Future research needs to clarify the relative importance of short and dynamic versus long-lived T cell-APC encounters for the outcome of T cell activation. Furthermore, a thorough understanding of the molecular events underlying the observed complex motility patterns will make these phenomena amenable for intervention, which might result in the identification of new types of immune modulating drugs.
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Affiliation(s)
- Peter Reichardt
- Junior Research Group of Immunodynamics, German Research Centre for Biotechnology (GBF), Braunschweig, Germany
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268
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Chuang WY, Ströbel P, Gold R, Nix W, Schalke B, Kiefer R, Opitz A, Klinker E, Müller-Hermelink HK, Marx A. A CTLA4high genotype is associated with myasthenia gravis in thymoma patients. Ann Neurol 2005; 58:644-8. [PMID: 16178018 DOI: 10.1002/ana.20577] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Myasthenia gravis (MG) in thymoma patients depends critically on intratumorous generation and export of mature autoreactive CD4+ T cells. Why non-MG thymomas fail to produce CD4+ T cells is unknown. We studied three single-nucleotide polymorphisms of the cytotoxic T-lymphocyte-associated antigen 4(CTLA4) gene in thymoma patients, nonthymoma early-onset MG patients, and control subjects. Surprisingly, the CTLA4high genotype +49A/A, which is protective against several autoimmune diseases, exerted a prominent predisposing effect to paraneoplastic MG in thymoma patients. The unusual disease association with a CTLA4high genotype implies a unique pathogenesis of paraneoplastic MG, with high CTLA4 levels possibly supporting the nontolerogenic selection of CD4+ T cells in MG-associated thymomas.
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Affiliation(s)
- Wen-Yu Chuang
- Institute of Pathology, University of Würzburg, Würzburg, Germany
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269
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Hogquist KA, Baldwin TA, Jameson SC. Central tolerance: learning self-control in the thymus. Nat Rev Immunol 2005; 5:772-82. [PMID: 16200080 DOI: 10.1038/nri1707] [Citation(s) in RCA: 423] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In the past few years, there has been a flurry of discoveries and advancements in our understanding of how the thymus prepares T cells to exist at peace in normal healthy tissue: that is, to be self-tolerant. In the thymus, one of the main mechanisms of T-cell central tolerance is clonal deletion, although the selection of regulatory T cells is also important and is gaining enormous interest. In this Review, we discuss the emerging consensus about which models of clonal deletion are most physiological, and we review recent data that define the molecular mechanisms of central tolerance.
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Affiliation(s)
- Kristin A Hogquist
- Center for Immunology, Department of Laboratory Medicine and Pathology, University of Minnesota, 312 Church Street South East, Minneapolis, Minnesota 55455, USA.
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270
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Bunin A, Khwaja FW, Kersh GJ. Regulation of Bim by TCR signals in CD4/CD8 double-positive thymocytes. THE JOURNAL OF IMMUNOLOGY 2005; 175:1532-9. [PMID: 16034091 DOI: 10.4049/jimmunol.175.3.1532] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Bim, a BH3-only Bcl-2 family member, is required for apoptosis of thymocytes in response to negative selection signals. Regulation of the apoptotic activity of Bim during negative selection is not understood. In this study we demonstrate that in murine thymocytes undergoing apoptosis in response to anti-CD3epsilon injection, levels of Bim protein expression do not change. In immature thymocytes, Bim is associated with mitochondria before stimulation and is not regulated by a change in subcellular localization during apoptosis. We also show that Bim(EL) is rapidly phosphorylated in thymocytes in response to CD3epsilon cross-linking both in vivo and in vitro, and that phosphorylation is sustained for at least 24 h. Analysis of MHC-deficient mice shows that phosphorylation of Bim occurs in CD4/CD8 double-positive thymocytes and does not depend on activation of mature T cells. We also find that TCR cross-linking on thymocytes induces an increase in the proportion of Bcl-x(L) bound to Bim at late time points. Our results favor a model in which strong TCR signals regulate the apoptotic activity of Bim by phosphorylation and subsequent changes in binding to Bcl-x(L) in immature thymocytes.
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MESH Headings
- Animals
- Antibodies, Monoclonal/administration & dosage
- Apoptosis/immunology
- Apoptosis Regulatory Proteins
- Bcl-2-Like Protein 11
- CD3 Complex/immunology
- CD4 Antigens/biosynthesis
- CD8 Antigens/biosynthesis
- Carrier Proteins/biosynthesis
- Carrier Proteins/metabolism
- Cross-Linking Reagents/metabolism
- Dexamethasone/administration & dosage
- Dose-Response Relationship, Immunologic
- Injections, Intravenous
- Membrane Proteins/biosynthesis
- Membrane Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microtubules/metabolism
- Models, Immunological
- Phosphorylation
- Protein Binding/drug effects
- Protein Binding/immunology
- Proto-Oncogene Proteins/biosynthesis
- Proto-Oncogene Proteins/metabolism
- Proto-Oncogene Proteins c-bcl-2/metabolism
- Receptors, Antigen, T-Cell/immunology
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/physiology
- Signal Transduction/immunology
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Thymus Gland/cytology
- Thymus Gland/immunology
- Thymus Gland/metabolism
- bcl-X Protein
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Affiliation(s)
- Anna Bunin
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
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271
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Thien CBF, Blystad FD, Zhan Y, Lew AM, Voigt V, Andoniou CE, Langdon WY. Loss of c-Cbl RING finger function results in high-intensity TCR signaling and thymic deletion. EMBO J 2005; 24:3807-19. [PMID: 16211006 PMCID: PMC1276723 DOI: 10.1038/sj.emboj.7600841] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 09/19/2005] [Indexed: 01/15/2023] Open
Abstract
Signaling from the T-cell receptor (TCR) in thymocytes is negatively regulated by the RING finger-type ubiquitin ligase c-Cbl. To further investigate this regulation, we generated mice with a loss-of-function mutation in the c-Cbl RING finger domain. These mice exhibit complete thymic deletion by young adulthood, which is not caused by a developmental block, lack of progenitors or peripheral T-cell activation. Rather, this phenotype correlates with greatly increased expression of the CD5 and CD69 activation markers and increased sensitivity to anti-CD3-induced cell death. Thymic loss contrasts the normal fate of the c-Cbl-/- thymus, even though thymocytes from both mutant mice show equivalent enhancement in proximal TCR signaling, Erk activation and calcium mobilization. Remarkably, only the RING finger mutant thymocytes show prominent TCR-directed activation of Akt. We show that the mutant c-Cbl protein itself is essential for activating this pathway by recruiting the p85 regulatory subunit of PI 3-kinase. This study provides a unique model for analyzing high-intensity TCR signals that cause thymocyte deletion and highlights multiple roles of c-Cbl in regulating this process.
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MESH Headings
- Amino Acid Substitution
- Animals
- Antigens, CD/analysis
- Antigens, Differentiation, T-Lymphocyte/analysis
- Apoptosis
- CD3 Complex/analysis
- CD5 Antigens/analysis
- Extracellular Signal-Regulated MAP Kinases/analysis
- Lectins, C-Type
- Lymphocyte Specific Protein Tyrosine Kinase p56(lck)/analysis
- Mice
- Mice, Transgenic
- Mutation
- Phosphatidylinositol 3-Kinases/metabolism
- Protein Structure, Tertiary
- Proto-Oncogene Proteins c-cbl/chemistry
- Proto-Oncogene Proteins c-cbl/genetics
- Proto-Oncogene Proteins c-cbl/physiology
- Receptors, Antigen, T-Cell/immunology
- Receptors, Antigen, T-Cell/physiology
- Signal Transduction
- Thymus Gland/immunology
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Affiliation(s)
- Christine B F Thien
- School of Surgery and Pathology, University of Western Australia, Crawley, Australia
| | - Frøydis D Blystad
- School of Surgery and Pathology, University of Western Australia, Crawley, Australia
| | - Yifan Zhan
- The Walter and Eliza Hall Institute of Medical Research, Royal Parade, Melbourne, Australia
| | - Andrew M Lew
- The Walter and Eliza Hall Institute of Medical Research, Royal Parade, Melbourne, Australia
| | - Valentina Voigt
- Centre for Experimental Immunology, The Lions Eye Institute, Nedlands, Australia
| | | | - Wallace Y Langdon
- School of Surgery and Pathology, University of Western Australia, Crawley, Australia
- School of Surgery and Pathology, University of Western Australia, Crawley, WA 6009, Australia. Tel.: +61 8 9346 2939; Fax: +61 8 9346 2891; E-mail:
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272
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Zhang N, Hartig H, Dzhagalov I, Draper D, He YW. The role of apoptosis in the development and function of T lymphocytes. Cell Res 2005; 15:749-69. [PMID: 16246265 DOI: 10.1038/sj.cr.7290345] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Apoptosis plays an essential role in T cell biology. Thymocytes expressing nonfunctional or autoreactive TCRs are eliminated by apoptosis during development. Apoptosis also leads to the deletion of expanded effector T cells during immune responses. The dysregulation of apoptosis in the immune system results in autoimmunity, tumorogenesis and immunodeficiency. Two major pathways lead to apoptosis: the intrinsic cell death pathway controlled by Bcl-2 family members and the extrinsic cell death pathway controlled by death receptor signaling. These two pathways work together to regulate T lymphocyte development and function.
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Affiliation(s)
- Nu Zhang
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
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273
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Baldwin TA, Sandau MM, Jameson SC, Hogquist KA. The timing of TCR alpha expression critically influences T cell development and selection. ACTA ACUST UNITED AC 2005; 202:111-21. [PMID: 15998791 PMCID: PMC2212895 DOI: 10.1084/jem.20050359] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Sequential rearrangement of the T cell receptor for antigen (TCR) beta and alpha chains is a hallmark of thymocyte development. This temporal control is lost in TCR transgenics because the alpha chain is expressed prematurely at the CD4- CD8- double negative (DN) stage. To test the importance of this, we expressed the HY alpha chain at the physiological CD4+ CD8+ double positive (DP) stage. The reduced DP and increased DN cellularity typically seen in TCR transgenics was not observed when the alpha chain was expressed at the appropriate stage. Surprisingly, antigen-driven selection events were also altered. In male mice, thymocyte deletion now occurred at the single positive or medullary stage. In addition, no expansion of CD8 alpha alpha intestinal intraepithelial lymphocytes (IELs) was observed, despite the fact that HY transgenics have been used to model IEL development. Collectively, these data establish the importance of proper timing of TCR expression in thymic development and selection and emphasize the need to use models that most accurately reflect the physiologic process.
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Affiliation(s)
- Troy A Baldwin
- Center for Immunology, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA
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274
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Azukizawa H, Sano S, Kosaka H, Sumikawa Y, Itami S. Prevention of toxic epidermal necrolysis by regulatory T cells. Eur J Immunol 2005; 35:1722-30. [PMID: 15909306 DOI: 10.1002/eji.200425773] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
To analyze immunoregulation of autoreactive T cells specific for epidermal skin antigens, we crossed transgenic mice expressing ovalbumin selectively in keratinocytes under the keratin 5 promoter (K5-mOVA) with mice expressing a K(b)-restricted OVA-specific T cell receptor transgene (OT-I). In athymic double-transgenic mice, OT-I cells developed extrathymically and, at 8-12 weeks of age, initiated severe epidermal damage mimicking toxic epidermal necrolysis (TEN). In contrast, euthymic double-transgenic mice showed thymic deletion of OT-I cells, had few of these cells in the periphery, and never developed skin changes mimicking TEN. Adoptive transfer of OT-I cells isolated from euthymic double-transgenic mice induced TEN in athymic K5-mOVA single-transgenic mice. This spontaneous disease in athymic double-transgenic mice was prevented by transferring lymph node cells from euthymic mice, but was not prevented when CD4(+) or CD25(+) cells were depleted from this population. Although purified CD4(+)CD25(+) cells scarcely prevented the skin disease induced by adoptive transfer of OT-I cells, they efficiently prevented the disease when co-transferred with CD11c(+) dendritic cells. These results suggested that thymus-derived regulatory T cells cooperate with CD11c(+) dendritic cells to prevent life-threatening skin damage such as TEN.
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Affiliation(s)
- Hiroaki Azukizawa
- Department of Dermatology, Course of Molecular Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan
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275
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Goodnow CC, Sprent J, Fazekas de St Groth B, Vinuesa CG. Cellular and genetic mechanisms of self tolerance and autoimmunity. Nature 2005; 435:590-7. [PMID: 15931211 DOI: 10.1038/nature03724] [Citation(s) in RCA: 470] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The mammalian immune system has an extraordinary potential for making receptors that sense and neutralize any chemical entity entering the body. Inevitably, some of these receptors recognize components of our own body, and so cellular mechanisms have evolved to control the activity of these 'forbidden' receptors and achieve immunological self tolerance. Many of the genes and proteins involved are conserved between humans and other mammals. This provides the bridge between clinical studies and mechanisms defined in experimental animals to understand how sets of gene products coordinate self-tolerance mechanisms and how defects in these controls lead to autoimmune disease.
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276
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Switzer KC, McMurray DN, Chapkin RS. Effects of dietary n-3 polyunsaturated fatty acids on T-cell membrane composition and function. Lipids 2005; 39:1163-70. [PMID: 15736911 DOI: 10.1007/s11745-004-1343-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Dietary n-3 PUFA have been shown to attenuate T-cell-mediated inflammation, in part, by suppressing T-cell activation and proliferation. n-3 PUFA have also been shown to promote apoptosis, another important mechanism for the prevention of chronic inflammation by maintaining T-cell homeostasis through the contraction of populations of activated T cells. Recent studies have specifically examined Fas death receptor-mediated activation-induced cell death (AICD), since it is the form of apoptosis associated with peripheral T-cell deletion involved in immunological tolerance and T-cell homeostasis. Data from our laboratory indicate that n-3 PUFA promote AICD in T helper 1 polarized cells, which are the mediators of chronic inflammation. Since Fas and components of the death-inducing signaling complex are recruited to plasma membrane microdomains (rafts), the effect of dietary n-3 PUFA on raft composition and resident protein localization has been the focus of recent investigations. Indeed, there is now compelling evidence that dietary n-3 PUFA are capable of modifying the composition of T-cell membrane microdomains (rafts). Because the lipids found in membrane microdomains actively participate in signal transduction pathways, these results support the hypothesis that dietary n-3 PUFA influence signaling complexes and modulate T-cell cytokinetics in vivo by altering T-cell raft composition.
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Affiliation(s)
- Kirsten C Switzer
- Molecular and Cell Biology Section, Faculty of Nutrition, Texas A&M University Health Science Center, College Station, Texas 77843-2471, USA
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277
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Reed-Loisel LM, Sullivan BA, Laur O, Jensen PE. An MHC Class Ib-Restricted TCR That Cross-Reacts with an MHC Class Ia Molecule. THE JOURNAL OF IMMUNOLOGY 2005; 174:7746-52. [PMID: 15944277 DOI: 10.4049/jimmunol.174.12.7746] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
TCR transgenic 6C5 T cells recognize an insulin B chain epitope presented by the nonclassical class I MHC molecule, Qa-1(b). Positive selection of these T cells was shown previously to require Qa-1(b). Despite dedicated specificity for Qa-1(b), evidence presented in the current study indicates that 6C5 T cells can cross-recognize a classical class I molecule. Clonal deletion was observed unexpectedly in 6C5.H-2(bxq) mice, which do not express I-E MHC class II molecules and thus should not be subject to superantigen-mediated negative selection. 6C5 T cells were observed to respond in vivo and in vitro to spleen cells from allogeneic H-2(q) mice, and specificity was mapped to D(q). Evidence was obtained for direct recognition of D(q), rather than indirect presentation of a D(q)-derived peptide presented by Qa-1(b). Polyclonal CD8(+) T cells from class Ia-deficient K(b)D(b-/-) mice reacted in vitro to allogeneic spleen cells with an apparent frequency comparable to conventional class Ia-restricted T cells. Our results provide a clear example of a Qa-1-specific TCR that can cross-react with a class Ia molecule and evidence supporting the idea that this may be a common property of T cells selected by class Ib molecules.
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MESH Headings
- Animals
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Cell Line, Transformed
- Cell Line, Tumor
- Cell Lineage/genetics
- Cell Lineage/immunology
- Clonal Deletion
- Crosses, Genetic
- H-2 Antigens/genetics
- H-2 Antigens/immunology
- H-2 Antigens/metabolism
- Histocompatibility Antigens Class I/genetics
- Histocompatibility Antigens Class I/immunology
- Histocompatibility Antigens Class I/metabolism
- Mammary Tumor Virus, Mouse/immunology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
- Superantigens/genetics
- Superantigens/immunology
- Superantigens/metabolism
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
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Affiliation(s)
- Lisa M Reed-Loisel
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
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278
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Catlett IM, Hedrick SM. Suppressor of cytokine signaling 1 is required for the differentiation of CD4+ T cells. Nat Immunol 2005; 6:715-21. [PMID: 15924143 DOI: 10.1038/ni1211] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2004] [Accepted: 04/14/2005] [Indexed: 01/08/2023]
Abstract
Suppressor of cytokine signaling 1 (Socs1) is critical for the regulation of interferon-gamma responses and T cell homeostasis. Although the presentation of the inflammatory disease of Socs1-deficient mice is complex, we have tested here the hypothesis that it originates from inappropriate T cell development and the appearance of autoreactive T cells. Socs1-deficient T cell receptor-transgenic mice showed severely impaired positive selection and a substantial alteration in CD4-CD8 T cell fate specification. These defects were dependent on interferon-gamma. Moreover, negative selection was also impaired, suggesting that autoimmunity contributes to the disease observed in Socs1(-/-) mice. We conclude that the constitutive expression of Socs1 in the thymus protects the process of thymic development and selection from the effects of systemic inflammation.
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Affiliation(s)
- Ian M Catlett
- The University of California San Diego, La Jolla, California 92093-0377, USA
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279
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Vacchio MS, Hodes RJ. Fetal expression of Fas ligand is necessary and sufficient for induction of CD8 T cell tolerance to the fetal antigen H-Y during pregnancy. THE JOURNAL OF IMMUNOLOGY 2005; 174:4657-61. [PMID: 15814689 DOI: 10.4049/jimmunol.174.8.4657] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Interaction of Fas with Fas ligand (FasL) is known to play a role in peripheral tolerance mediated by clonal deletion of Ag-specific T cells. We have assessed the requirement for Fas/FasL interactions during induction of tolerance to the fetus. Using H-Y-specific TCR transgenic mice, we have previously demonstrated that exposure of maternal T cells to H-Y expressed by male fetuses results in deletion of 50% of H-Y-specific maternal T cells. The remaining H-Y-specific T cells were hyporesponsive to H-Y as assayed by decreased proliferative ability and CTL activity. To determine whether Fas/FasL interactions contribute to induction of maternal T cell tolerance, responsiveness to fetal H-Y was assessed in H-Y-specific TCR transgenic pregnant females that were deficient in functional Fas or FasL. Surprisingly, both deletion and nondeletion components of tolerance were abrogated in TCR transgenic H-Y-specific lpr (Fas-deficient) or gld (FasL-deficient) pregnant females. Experiments further revealed that expression of FasL by the fetus, but not by the mother, is necessary and sufficient for both components of maternal T cell tolerance to fetal Ags. Fas interaction with fetal FasL is thus critical for both deletion and hyporesponsiveness of H-Y-reactive CD8+ T cells during pregnancy.
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Affiliation(s)
- Melanie S Vacchio
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1360, USA.
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280
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Sehra S, Patel D, Kusam S, Wang ZY, Chang CH, Dent AL. A role for caspases in controlling IL-4 expression in T cells. THE JOURNAL OF IMMUNOLOGY 2005; 174:3440-6. [PMID: 15749878 DOI: 10.4049/jimmunol.174.6.3440] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Although caspase activation is critical for T cell proliferation following activation, the role of caspases in T cell differentiation is unclear. In this study, we have examined the effect of inhibition of caspases on the process of Th1/Th2 differentiation. Naive CD4+ T cells activated under neutral differentiation conditions in the presence of the pan caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp (Z-VAD) fluoromethylketone showed increased Th2 cell differentiation concomitant with an up-regulation of GATA-3. Z-VAD induced optimal Th2 differentiation when T cells were stimulated under strong primary activation conditions. Treatment of naive CD4+ T cells with Z-VAD under strong activation conditions led to a 6-fold increase in IL-4 mRNA compared with control-treated T cells. The Z-VAD-induced increase in IL-4 transcription occurred within 24 h of activation and was independent of Stat6. IFN-gamma mRNA expression was not affected by Z-VAD at the 24-h time point. Z-VAD did not augment IL-4 expression from a committed Th2 cell, suggesting that caspases regulate IL-4 expression specifically during primary T cell activation. Z-VAD did not augment IL-12-driven Th1 differentiation. Activation of T cells in the presence of Z-VAD led to a specific increase in the expression of the transcription factor c-fos. Lastly, retrovirus-mediated expression of the antiapoptotic protein Bcl-2 resulted in an enhancement of Th2 cytokine expression, suggesting that inhibition of caspase activation by Bcl-2 can also modulate IL-4 expression. These findings reveal a novel regulatory mechanism of cytokine expression by caspases, and may explain how signaling pathways that inhibit apoptosis tend to promote Th2 differentiation.
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Affiliation(s)
- Sarita Sehra
- Department of Microbiology and Immunology, The Walther Oncology Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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281
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Yu P, Lee Y, Liu W, Krausz T, Chong A, Schreiber H, Fu YX. Intratumor depletion of CD4+ cells unmasks tumor immunogenicity leading to the rejection of late-stage tumors. ACTA ACUST UNITED AC 2005; 201:779-91. [PMID: 15753211 PMCID: PMC2212829 DOI: 10.1084/jem.20041684] [Citation(s) in RCA: 334] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Tumor environment can be critical for preventing the immunological destruction of antigenic tumors. We have observed a selective accumulation of CD4(+)CD25(+) T cells inside tumors. In a murine fibrosarcoma L(d)-expressing Ag104, these cells made up the majority of tumor-infiltrating lymphocytes at the late stage of tumor progression, and their depletion during the effector phase, rather than priming phase, successfully enhanced antitumor immunity. We show here that CD4(+)CD25(+) T cells suppressed the proliferation and interferon-gamma production of CD8(+) T cells in vivo at the local tumor site. Blockade of the effects of IL-10 and TGF-beta partially reversed the suppression imposed by the CD4(+) cells. Furthermore, local depletion of CD4(+) cells inside the tumor resulted in a change of cytokine milieu and led to the eradication of well-established highly aggressive tumors and the development of long-term antitumor memory. Therefore, CD4(+)CD25(+) T cells maintained an environment in the tumor that concealed the immunogenicity of tumor cells to permit progressive growth of antigenic tumors. Our study illustrates that the suppression of antitumor immunity by regulatory T cells occurs predominantly at the tumor site, and that local reversal of suppression, even at a late stage of tumor development, can be an effective treatment for well-established cancers.
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Affiliation(s)
- Ping Yu
- The Committee on Immunology, University of Chicago, Chicago, IL 60637, USA.
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282
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Redmond WL, Marincek BC, Sherman LA. Distinct requirements for deletion versus anergy during CD8 T cell peripheral tolerance in vivo. THE JOURNAL OF IMMUNOLOGY 2005; 174:2046-53. [PMID: 15699134 DOI: 10.4049/jimmunol.174.4.2046] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Activation of naive T cells by quiescent APCs results in tolerance through deletion and anergy. The underlying basis for these distinct fates is unclear. Using clone 4 TCR transgenic animals as a source of naive CD8 T cells, we examined the requirements for peripheral deletion in vivo. Our results demonstrate that independent of the amount of Ag used for stimulation, a single dose was insufficient to achieve complete clonal deletion. Instead, further antigenic exposure was required to completely eliminate all of the activated T cells. Additionally, consecutive stimulations with low doses of Ag were highly effective in promoting deletion. In contrast, although stimulation with high doses of Ag initially led to the apoptosis of many of the activated T cells, it induced hyporesponsiveness in a portion of the responding cells, thereby sparing them from further activation and deletion. These data explain why some conditions promote tolerance through clonal deletion whereas others promote anergy. Furthermore, these data provide a framework to devise protocols for effective deletion of potentially autoreactive T cells.
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Affiliation(s)
- William L Redmond
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
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283
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Abstract
"Nature has provided, in the white corpuscles as you call them-in the phagocytes as we call them-a natural means of devouring and destroying all disease germs. There is at bottom only one genuinely scientific treatment for all diseases, and that is to stimulate the phagocytes." So opined B.B. in G.B. Shaw's The Doctor's Dilemma in a dramatic restatement of a key portion of Ilya Metchnikoff's Nobel Prize address: "Whenever the organism enjoys immunity, the introduction of infectious microbes is followed by the accumulation of mobile cells, of white corpuscles of the blood in particular which absorb the microbes and destroy them. The white corpuscles and the other cells capable of doing this have been designated 'phagocytes,' (i.e., devouring cells) and the whole function that ensures immunity has been given the name of 'phagocytosis'". Based on these insights into the foundation of resistance to infectious disease, Metchnikoff was awarded the 1908 Nobel Prize in Physiology or Medicine together with Paul Ehrlich (Fig. 1). Although both were cited for discoveries in immunity, the contributions of the two men seem worlds apart. Ehrlich's studies did not deal with generic responses to infection, but rather with the highly specific nature of antibodies and their relationship to the cells producing them: "As the cell receptor is obviously preformed, and the artificially produced antitoxin only the consequence, i.e. secondary, one can hardly fail to assume that the antitoxin is nothing else but discharged components of the cell, namely receptors discharged in excess". But biological systems are just that-systems-and the parts need to work together. And so we arrive, a century later, at an appreciation for just how intimately related these two seemingly disparate aspects of host defense really are.
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Affiliation(s)
- Ronald N Germain
- Lymphocyte Biology Section, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
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284
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Redmond WL, Sherman LA. Peripheral Tolerance of CD8 T Lymphocytes. Immunity 2005; 22:275-84. [PMID: 15780985 DOI: 10.1016/j.immuni.2005.01.010] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Revised: 01/10/2005] [Accepted: 01/13/2005] [Indexed: 01/18/2023]
Abstract
Whereas high-avidity recognition of peptide-MHC complexes by developing T cells in the thymus results in deletion and promotes self-tolerance, such recognition by mature T cells in the periphery results in activation and clonal expansion. This dichotomy represents the basis of a dilemma that has stumped immunologists for many years, how are self-specific T cells tolerized in the periphery? There appear to be two important criteria used to achieve this goal. The first is that in the absence of inflammatory pathogens, tolerance is promoted when T cells recognize antigen presented by quiescent dendritic cells (DCs) expressing low levels of costimulatory molecules. A second critical factor that defines "self" and drives tolerance through deletion, anergy, or suppression is the persistence of antigen.
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Affiliation(s)
- William L Redmond
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA
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285
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Kwon H, Jun HS, Khil LY, Yoon JW. Role of CTLA-4 in the activation of single- and double-positive thymocytes. THE JOURNAL OF IMMUNOLOGY 2005; 173:6645-53. [PMID: 15557155 DOI: 10.4049/jimmunol.173.11.6645] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
CTLA-4, a homologue of CD28, is a negative regulator of T cell activation in the periphery and is transiently expressed on the cell surface after T cell activation. However, the role of CTLA-4 in T cell activation in the thymus is not clear. This investigation was initiated to determine the role of CTLA-4 in the activation of CD4(+)CD8(+) double-positive (DP) and CD4(+)CD8(-) and CD4(-)CD8(+) single-positive (SP) thymocytes using fetal thymic organ cultures (FTOC) of MHC class II-restricted, OVA(323-339)-restricted TCR transgenic mice (DO11.10). We found that treatment of the FTOC with anti-CTLA-4-blocking Ab during activation with OVA(323-339) increased the proportion and number of DP thymocytes, but decreased the proportion and number of SP thymocytes compared with OVA(323-339)-stimulated FTOC without anti-CTLA-4 Ab treatment. In addition, anti-CTLA-4 Ab treatment inhibited OVA(323-339)-induced expression of the early activation marker, CD69, in DP thymocytes, but increased CD69 in SP thymocytes. Similarly, CTLA-4 blockage decreased phosphorylation of ERK in DP thymocytes by Ag-specific TCR engagement, but increased phosphorylation of ERK in SP thymocytes. CTLA-4 blockage inhibited deletion of DP thymocytes treated with a high dose of OVA(323-339), whereas CTLA-4 blockage did not inhibit deletion of DP thymocytes treated with a low dose of OVA(323-339). We conclude that CTLA-4 positively regulates the activation of DP thymocytes, resulting in their deletion, whereas blocking CTLA-4 suppresses the activation of DP thymocytes, leading to inhibition of DP thymocyte deletion. In contrast, CTLA-4 negatively regulates the activation of SP thymocytes.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antibodies, Blocking/pharmacology
- Antigens, CD
- Antigens, Differentiation/biosynthesis
- Antigens, Differentiation/genetics
- Antigens, Differentiation/immunology
- Antigens, Differentiation/physiology
- CD4 Antigens/biosynthesis
- CD8 Antigens/biosynthesis
- CTLA-4 Antigen
- Clonal Deletion
- Down-Regulation/immunology
- Epitopes, T-Lymphocyte/immunology
- Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Female
- Lymphocyte Activation/immunology
- Lymphocyte Count
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Molecular Sequence Data
- Organ Culture Techniques
- Receptors, Antigen, T-Cell/immunology
- Receptors, Antigen, T-Cell/metabolism
- Signal Transduction/immunology
- T-Lymphocyte Subsets/enzymology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Thymus Gland/cytology
- Thymus Gland/enzymology
- Thymus Gland/immunology
- Thymus Gland/metabolism
- Up-Regulation/immunology
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Affiliation(s)
- Hyokjoon Kwon
- Julia McFarlane Diabetes Research Center, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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286
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Wilson NS, Villadangos JA. Lymphoid organ dendritic cells: beyond the Langerhans cells paradigm. Immunol Cell Biol 2004; 82:91-8. [PMID: 14984600 DOI: 10.1111/j.1440-1711.2004.01216.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The immune system has developed mechanisms to detect and initiate responses to a continual barrage of immunological challenges. Dendritic cells (DC), a heterogeneous population of leucocytes, play a major role as immunosurveillance agents. To accomplish this function, DC are equipped with highly efficient mechanisms to detect pathogens, to capture, process and present antigens, and to initiate T-cell responses. These mechanisms are developmentally regulated during the DC life cycle in a process termed 'maturation', which was originally defined using Langerhans cells (LC), a DC type of the epidermis. LC exist in the skin in an immature state dedicated to capturing antigens, and in the subcutaneous lymph nodes in a mature state dedicated to presenting those antigens to T cells. The phenotypic changes undergone by LC during maturation, and the correlation of these changes with tissue localization, have been generally considered a paradigm for all DC. However, studies of the multiple DC types found in the lymphoid organs of mice and humans have revealed that most DC subsets do not follow the life cycle typified by LC. In this review we discuss the limitations of the 'LC paradigm' and suggest that this model should be revised to accommodate the heterogeneity of the DC system. We also discuss the implications of the maturational status of the DC subsets contained in the lymphoid organs for their putative roles in the induction of immune responses and the maintenance of peripheral tolerance.
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Affiliation(s)
- Nicholas S Wilson
- Immunology Division and Cooperative Research Centre for Vaccine Technology, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
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287
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288
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Delfino DV, Agostini M, Spinicelli S, Vito P, Riccardi C. Decrease of Bcl-xL and augmentation of thymocyte apoptosis in GILZ overexpressing transgenic mice. Blood 2004; 104:4134-41. [PMID: 15319285 DOI: 10.1182/blood-2004-03-0920] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glucocorticoids promote thymocyte apoptosis and modulate transcription of numerous genes. GILZ (glucocorticoid-induced leucine zipper), being one of them, is strongly up-regulated in the thymus. To elucidate its function we generated transgenic mice overexpressing it specifically in the T-cell lineage and characterized its influence on thymus function. In young adult transgenic mice CD4(+)CD8(+) thymocyte number was significantly decreased and ex vivo thymocyte apoptosis was increased. Apoptotic pathway analysis detected reduced antiapoptotic B-cell leukemia XL (Bcl-xL) expression and increased activation of caspase-8 and caspase-3. Time-course experiments showed that in wild-type (WT) thymocytes GILZ up-regulation was followed by sequential Bcl-xL decreased expression and activation of caspase-8 and of caspase-3. Moreover, GILZ delivered inside WT thymocytes by a fusion protein with the transactivator of transcription (TAT) peptide decreased Bcl-xL and promoted their apoptosis. In aged mice perturbation of thymic subset numbers was amplified over time, as demonstrated by a further decrease in CD4(+)CD8(+) cells and increases in CD4(+)CD8(-), CD4(-)CD8(-), and CD8(+)CD4(-) cell counts. These results support the hypothesis that GILZ participates in the regulation of thymocyte apoptosis by glucocorticoids.
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Affiliation(s)
- Domenico Vittorio Delfino
- Section of Pharmacology, Department of Clinical and Experimental Medicine, University of Perugia, Via del Giochetto, 06122 Perugia, Italy.
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289
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Murakami N, Yokomizo T, Okuno T, Shimizu T. G2A is a proton-sensing G-protein-coupled receptor antagonized by lysophosphatidylcholine. J Biol Chem 2004; 279:42484-91. [PMID: 15280385 DOI: 10.1074/jbc.m406561200] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
G2A (from G2 accumulation) is a G-protein-coupled receptor (GPCR) that regulates the cell cycle, proliferation, oncogenesis, and immunity. G2A shares significant homology with three GPCRs including ovarian cancer GPCR (OGR1/GPR68), GPR4, and T cell death-associated gene 8 (TDAG8). Lysophosphatidylcholine (LPC) and sphingosylphosphorylcholine (SPC) were reported as ligands for G2A and GPR4 and for OGR1 (SPC only), and a glycosphingolipid psychosine was reported as ligand for TDAG8. As OGR1 and GPR4 were reported as proton-sensing GPCRs (Ludwig, M. G., Vanek, M., Guerini, D., Gasser, J. A., Jones, C. E., Junker, U., Hofstetter, H., Wolf, R. M., and Seuwen, K. (2003) Nature 425, 93-98), we evaluated the proton-sensing function of G2A. Transient expression of G2A caused significant activation of the zif 268 promoter and inositol phosphate (IP) accumulation at pH 7.6, and lowering extracellular pH augmented the activation only in G2A-expressing cells. LPC inhibited the pH-dependent activation of G2A in a dose-dependent manner in these assays. Thus, G2A is another proton-sensing GPCR, and LPC functions as an antagonist, not as an agonist, and regulates the proton-dependent activation of G2A.
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Affiliation(s)
- Naoka Murakami
- Department of Biochemistry, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
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290
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Cao Q, Xia Y, Azadniv M, Crispe IN. The E2F-1 Transcription Factor Promotes Caspase-8 and Bid Expression, and Enhances Fas Signaling in T Cells. THE JOURNAL OF IMMUNOLOGY 2004; 173:1111-7. [PMID: 15240700 DOI: 10.4049/jimmunol.173.2.1111] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The immune system depends on the extensive proliferation of rare Ag-specific precursor T lymphocytes, followed by their differentiation, the delivery of effector function, and finally death by apoptosis. T cells that lack the E2F-1 transcription factor, which is activated as cells pass the restriction point and enter S phase, show defects in activation-induced cell death. We now report that E2F-1 increases the activity of an apoptotic pathway that is important in murine primary T cells. Thus, E2F-1 promotes the transcription of Bid, a molecule that links death receptor signaling to the activation of apoptotic mechanisms in mitochondria. It also promotes the transcription of caspase-8, the enzyme that cleaves and activates Bid. Enforced expression of Bid can partially restore apoptosis in E2F-1-deficient T cells. Thus, E2F-1 integrates cell cycle progression with apoptosis.
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Affiliation(s)
- Qingyu Cao
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, NY 14642, USA
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291
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292
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Mayerova D, Hogquist KA. Central tolerance to self-antigen expressed by cortical epithelial cells. THE JOURNAL OF IMMUNOLOGY 2004; 172:851-6. [PMID: 14707055 DOI: 10.4049/jimmunol.172.2.851] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The exposure of developing thymocytes to high-affinity self-Ag results in T cell tolerance. A predominant mechanism for this is clonal deletion; though receptor editing, anergy induction, and positive selection of regulatory T cells have also been described. It is unclear what signals are involved in determining different tolerance mechanisms. In particular, OT-I mice displayed receptor editing when the high-affinity self-Ag was expressed in cortical epithelial cells (cEC) using the human keratin 14 promoter. To test the hypothesis that receptor editing is a consequence of a unique instruction given by cEC presenting self-Ag, we created mice expressing the 2C and HY ligands under control of the keratin 14 promoter. Alternatively, we studied the fate of developing T cells in OT-I mice where Ag was presented by all thymic APC. Surprisingly, we found that the tolerance mechanism was not influenced by the APC subset involved in presentation. Clonal deletion was observed in 2C and HY models even when Ag was presented only by cEC; and receptor editing was observed in OT-I mice even when Ag was presented by all thymic APC. These results suggest that different TCRs show intrinsic differences in thymic tolerance mechanism.
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Affiliation(s)
- Dita Mayerova
- Center for Immunology, Department of Laboratory Medicine and Pathology, University of Minnesota, 312 Church Street SE, Minneapolis, MN 55455, USA
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293
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Abstract
Studies in both humans and rodent models provide new insight into key mechanisms regulating tolerance to self-molecules. There is evidence that tissue-specific molecules are expressed in the thymus and peripheral lymphoid tissues (PLTs) by specialized antigen-presenting cells (APCs), and that such expression is critical for self-tolerance. Insulin, a key hormone exclusively produced by pancreatic beta cells and a critical autoantigen in type 1 diabetes, provides an excellent example of a molecule with tissue-restricted expression that is ectopically expressed by APCs in both thymus and PLTs. APCs may play a role in insulin presentation in both the central and peripheral immune system. Functional data from several transgenic and knockout mouse models, some specific for the expression of insulin, help dissect the significance of self-molecule presentation by APCs and its role in autoimmune diabetes.
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Affiliation(s)
- Kamalaveni R Prabakar
- Immunogenetics Program, Diabetes Research Institute, University of Miami School of Medicine, 1450 NW 10th Avenue, Miami, FL 33136, USA
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294
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Teutsch SM, Booth DR, Bennetts BH, Heard RNS, Stewart GJ. Association of common T cell activation gene polymorphisms with multiple sclerosis in Australian patients. J Neuroimmunol 2004; 148:218-30. [PMID: 14975605 DOI: 10.1016/j.jneuroim.2003.12.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2003] [Revised: 12/03/2003] [Accepted: 12/03/2003] [Indexed: 12/15/2022]
Abstract
Susceptibility to multiple sclerosis (MS) may be influenced by the interaction of several genes within a biological pathway. T cell activation and costimulation may be potentially important in MS pathogenesis. We have therefore investigated associations between MS and polymorphisms in the CD152 (CTLA-4), CD28, CD80 and CD86 genes in Australian patients. We found no significant MS association with CTLA-4 exon 1 +49 alleles, and meta-analysis showed no significant association across nine comparable datasets (OR=1.04, p=0.54), nor with primary progressive MS across seven datasets (OR=1.19, p=0.21). Haplotype analysis showed a trend towards a decrease of the CTLA-4-1722C, -1577G, +49G haplotype in +49 G positive MS patients compared with controls (p=0.06). Screening of CD28, CD80 and CD86 genes identified novel polymorphisms in the putative promoter regions of CD28 (-372 G/A) and CD86 (exon 2 -359 deletionAAG). There was a significant increase of the CD28 -372 G allele frequency in MS patients vs. controls (p=0.045) and a trend towards a significant interaction between this allele and the CTLA-4 +49 G allele (OR=4.00, p=0.058). Our results suggest that the CTLA-4 +49 alone is not associated with overall susceptibility to MS, but may be important in clinical subsets of patients and/or may interact epistatically with other gene polymorphisms.
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Affiliation(s)
- Suzy M Teutsch
- Institute for Immunology and Allergy Research (Westmead Millennium Institute), Level 2 ICPMR, University of Sydney, Westmead Hospital, Westmead, NSW 2145, Australia.
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295
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Costello PS, Nicolas RH, Watanabe Y, Rosewell I, Treisman R. Ternary complex factor SAP-1 is required for Erk-mediated thymocyte positive selection. Nat Immunol 2004; 5:289-98. [PMID: 14770179 DOI: 10.1038/ni1038] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Accepted: 12/15/2003] [Indexed: 01/25/2023]
Abstract
Thymocyte selection and differentiation requires extracellular signal-regulated kinase (Erk) signaling, but transcription factor substrates of Erk in thymocytes are unknown. We have characterized the function of SAP-1 (Elk4), an Erk-regulated transcription factor, in thymocyte development. Early thymocyte development was normal, but single-positive thymocyte and peripheral T cell numbers were reduced, reflecting a T cell-autonomous defect. T cell receptor-induced activation of SAP-1 target genes such as Egr1 was substantially impaired in double-positive thymocytes, although Erk activation was normal. Analysis of T cell receptor transgenes showed that positive selection was reduced by 80-90% in SAP-1-deficient mice; heterozygous mice showed a moderate defect. Negative selection was unimpaired. SAP-1 thus directly links Erk signaling to the transcriptional events required for thymocyte positive selection.
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Affiliation(s)
- Patrick S Costello
- Transcription Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Fields, London WC2A 3PX, UK
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296
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Abstract
Apoptotic elimination of T cells at sites of inflammation or infiltration into tumors limits an effective immune response. T cell apoptosis can be initiated by a variety of triggers, including galectin-1, a soluble, secreted lectin that binds to oligosaccharide ligands on cell surface glycoproteins, or to oligosaccharide ligands on extracellular matrix glycoproteins in tissue stroma. Although galectin-1 has no transmembrane domain and is secreted from cells that make it, it is not clear if galectin-1 functions as a soluble death trigger in vivo. We examined the ability of stromal cells secreting galectin-1 to kill T cells. Although the stromal cells synthesized abundant galectin-1, the majority of the galectin-1 remained bound to the cell surface, and stromal cell-associated galectin-1 killed bound T cells. In contrast, insufficient amounts of functional galectin-1 were released from the stromal cells into the media to kill T cells in the absence of contact with stromal cells. However, when stromal cells were grown on Matrigel, a mixture of extracellular matrix proteins, or on permeable membranes above Matrigel, secreted galectin-1 bound to Matrigel and killed T cells without stromal cell contact. Ten-fold less galectin-1 on Matrigel was sufficient to kill adherent T cells compared with soluble galectin-1. These results demonstrate that galectin-1 in extracellular matrix is able to directly kill susceptible T cells. Because increased galectin-1 deposition in tumor stroma occurs with tumor progression in various types of cancer, galectin-1 in stroma may act locally in the apoptotic elimination of infiltrating T cells during an immune response.
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Affiliation(s)
- Jiale He
- Department of Pathology, UCLA School of Medicine, Los Angeles, California 90095, USA
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297
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Serreze DV, Holl TM, Marron MP, Graser RT, Johnson EA, Choisy-Rossi C, Slattery RM, Lieberman SM, DiLorenzo TP. MHC Class II Molecules Play a Role in the Selection of Autoreactive Class I-Restricted CD8 T Cells That Are Essential Contributors to Type 1 Diabetes Development in Nonobese Diabetic Mice. THE JOURNAL OF IMMUNOLOGY 2004; 172:871-9. [PMID: 14707058 DOI: 10.4049/jimmunol.172.2.871] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Development of autoreactive CD4 T cells contributing to type 1 diabetes (T1D) in both humans and nonobese diabetic (NOD) mice is either promoted or dominantly inhibited by particular MHC class II variants. In addition, it is now clear that when co-expressed with other susceptibility genes, some common MHC class I variants aberrantly mediate autoreactive CD8 T cell responses also essential to T1D development. However, it was unknown whether the development of diabetogenic CD8 T cells could also be dominantly inhibited by particular MHC variants. We addressed this issue by crossing NOD mice transgenically expressing the TCR from the diabetogenic CD8 T cell clone AI4 with NOD stocks congenic for MHC haplotypes that dominantly inhibit T1D. High numbers of functional AI4 T cells only developed in controls homozygously expressing NOD-derived H2(g7) molecules. In contrast, heterozygous expression of some MHC haplotypes conferring T1D resistance anergized AI4 T cells through decreased TCR (H2(b)) or CD8 expression (H2(q)). Most interestingly, while AI4 T cells exert a class I-restricted effector function, H2(nb1) MHC class II molecules can contribute to their negative selection. These findings provide insights to how particular MHC class I and class II variants interactively regulate the development of diabetogenic T cells and the TCR promiscuity of such autoreactive effectors.
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MESH Headings
- Animals
- Antigen-Presenting Cells/cytology
- Antigen-Presenting Cells/immunology
- Antigen-Presenting Cells/metabolism
- Autoantigens/immunology
- CD8-Positive T-Lymphocytes/immunology
- CD8-Positive T-Lymphocytes/metabolism
- CD8-Positive T-Lymphocytes/pathology
- Cell Differentiation/genetics
- Cell Differentiation/immunology
- Clonal Anergy/genetics
- Diabetes Mellitus, Type 1/genetics
- Diabetes Mellitus, Type 1/immunology
- Diabetes Mellitus, Type 1/pathology
- Down-Regulation/genetics
- Down-Regulation/immunology
- Female
- Genetic Carrier Screening
- Genetic Variation/immunology
- H-2 Antigens/genetics
- H-2 Antigens/immunology
- H-2 Antigens/metabolism
- Haplotypes
- Hematopoietic Stem Cells/cytology
- Hematopoietic Stem Cells/immunology
- Hematopoietic Stem Cells/metabolism
- Histocompatibility Antigens Class II/biosynthesis
- Histocompatibility Antigens Class II/genetics
- Histocompatibility Antigens Class II/physiology
- Histocompatibility Testing
- Lymphocyte Activation/genetics
- Male
- Mice
- Mice, Inbred NOD
- Mice, Transgenic
- Receptors, Antigen, T-Cell/biosynthesis
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/physiology
- Signal Transduction/genetics
- Signal Transduction/immunology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- T-Lymphocyte Subsets/pathology
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Affiliation(s)
- David V Serreze
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA.
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298
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Zarrinpar A, Park SH, Lim WA. Optimization of specificity in a cellular protein interaction network by negative selection. Nature 2003; 426:676-80. [PMID: 14668868 DOI: 10.1038/nature02178] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2003] [Accepted: 10/23/2003] [Indexed: 12/13/2022]
Abstract
Most proteins that participate in cellular signalling networks contain modular protein-interaction domains. Multiple versions of such domains are present within a given organism: the yeast proteome, for example, contains 27 different Src homology 3 (SH3) domains. This raises the potential problem of cross-reaction. It is generally thought that isolated domain-ligand pairs lack sufficient information to encode biologically unique interactions, and that specificity is instead encoded by the context in which the interaction pairs are presented. Here we show that an isolated peptide ligand from the yeast protein Pbs2 recognizes its biological partner, the SH3 domain from Sho1, with near-absolute specificity--no other SH3 domain present in the yeast genome cross-reacts with the Pbs2 peptide, in vivo or in vitro. Such high specificity, however, is not observed in a set of non-yeast SH3 domains, and Pbs2 motif variants that cross-react with other SH3 domains confer a fitness defect, indicating that the Pbs2 motif might have been optimized to minimize interaction with competing domains specifically found in yeast. System-wide negative selection is a subtle but powerful evolutionary mechanism to optimize specificity within an interaction network composed of overlapping recognition elements.
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Affiliation(s)
- Ali Zarrinpar
- Program in Biological Sciences, University of California, San Francisco, 600 16th Street, San Francisco, California 94143-2240, USA
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299
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Boldizsár F, Pálinkás L, Bartis D, Németh P, Berki T. Antigen and glucocorticoid hormone (GC) induce positive selection of DP thymocytes in a TcR transgenic mouse model. Immunol Lett 2003; 90:97-102. [PMID: 14687711 DOI: 10.1016/j.imlet.2003.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Thymocyte maturation in the thymus is controlled by stromal and humoral components. Among the humoral regulators locally produced glucocorticoids (GCs) seem to have a key role in the positive selection of thymocytes. Our previous studies have shown that the administration of GCs or the stimulation through the CD3 complex can induce apoptosis of double positive (DP) cells, but the combined presence of these stimuli induces positive selection. In this work our aim was to investigate the effects of antigen exposure and synthetic GC hormone (dexamethasone, DX) administration on the selection processes of DP cells in TcR transgenic mice. In our model, AND-pigeon cytochrome c (PCC)-specific I-E(k) (MHC-II) restricted Vbeta3, Valpha11 TcR expressing transgenic mice were treated with PCC, with high or low dose DX, or with PCC and DX together, followed by the analysis of total thymocyte numbers, thymocyte composition, with regard to their CD69, Vbeta3 and Annexin V expression. The administration of PCC and/or DX for 2 days resulted in a decreased DP cell number and a significantly increased CD4 SP cell ratio. However, in both cases the total thymocyte numbers decreased. CD69 expression increased on both DP and CD4 SP cells after PCC and/or DX treatments. We found that after DX or combined treatment, the percentage of Annexin V positive cells increased. The ratio of Vbeta3 TcR bearing DP thymocytes showed no change after DX or PCC administrations alone, but it decreased significantly after combined treatment. MHC-II bound PCC peptides in the presence of GCs enhanced the maturation of Vbeta3+ DP cells into CD4 SP stage, therefore, the Vbeta3- cells remained mostly in the DP immature stage. These data indicate that both antigen and low dose GC alone are capable of inducing positive selection of DP cells, but together they gave a stronger effect in promoting positive selection. From these we conclude that GCs influence the maturation and selection processes of thymocytes.
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MESH Headings
- Animals
- Antigens/immunology
- Antigens, CD/metabolism
- Antigens, Differentiation, T-Lymphocyte/metabolism
- Apoptosis/drug effects
- Cell Count
- Cell Differentiation/drug effects
- Columbidae
- Cytochromes c/immunology
- Dexamethasone/pharmacology
- Lectins, C-Type
- Mice
- Mice, Transgenic
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Thymus Gland/cytology
- Thymus Gland/drug effects
- Thymus Gland/immunology
- Thymus Gland/metabolism
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Affiliation(s)
- Ferenc Boldizsár
- Department of Immunology and Biotechnology, Faculty of Medicine, University of Pécs, Pécs, Szigeti út 12, H-7624 Pécs, Hungary.
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300
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Abstract
Antigen binding to T cell receptors is a critical step in an immune response. Detection and characterization of rare populations of T cells enhances our ability to understand and treat disease
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Affiliation(s)
- Jill E Slansky
- Department of Immunology at the University of Colorado Health Sciences Center in Denver, Colorado, USA.
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