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Myers DR, Zikherman J, Roose JP. Tonic Signals: Why Do Lymphocytes Bother? Trends Immunol 2017; 38:844-857. [PMID: 28754596 DOI: 10.1016/j.it.2017.06.010] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 06/23/2017] [Accepted: 06/27/2017] [Indexed: 01/09/2023]
Abstract
Since the 1990s it has been known that B and T lymphocytes exhibit low-level, constitutive signaling in the basal state (tonic signaling). These lymphocytes display a range of affinity for self, which in turn generates a range of tonic signaling. Surprisingly, what signaling pathways are active in the basal state and the functional relevance of the observed tonic signaling heterogeneity remain open questions today. Here we summarize what is known about the mechanistic and functional details of tonic signaling. We highlight recent advances that have increased our understanding of how the amount of tonic signal impacts immune function, describing novel tools that have moved the field forward and toward a molecular understanding of tonic signaling.
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Affiliation(s)
- Darienne R Myers
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA 94143, USA
| | - Julie Zikherman
- Division of Rheumatology, Rosalind Russell and Ephraim P. Engleman Arthritis Research Center, Department of Medicine, University of California, San Francisco, CA 94143, USA
| | - Jeroen P Roose
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA 94143, USA.
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2
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Palmer VL, Aziz-Seible R, Kassmeier MD, Rothermund M, Perry GA, Swanson PC. VprBP Is Required for Efficient Editing and Selection of Igκ+ B Cells, but Is Dispensable for Igλ+ and Marginal Zone B Cell Maturation and Selection. THE JOURNAL OF IMMUNOLOGY 2015; 195:1524-37. [PMID: 26150531 DOI: 10.4049/jimmunol.1500952] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 06/02/2015] [Indexed: 01/01/2023]
Abstract
B cell development past the pro-B cell stage in mice requires the Cul4-Roc1-DDB1 E3 ubiquitin ligase substrate recognition subunit VprBP. Enforced Bcl2 expression overcomes defects in distal VH-DJH and secondary Vκ-Jκ rearrangement associated with VprBP insufficiency in B cells and substantially rescues maturation of marginal zone and Igλ(+) B cells, but not Igκ(+) B cells. In this background, expression of a site-directed Igκ L chain transgene increases Igκ(+) B cell frequency, suggesting VprBP does not regulate L chain expression from a productively rearranged Igk allele. In site-directed anti-dsDNA H chain transgenic mice, loss of VprBP function in B cells impairs selection of Igκ editor L chains typically arising through secondary Igk rearrangement, but not selection of Igλ editor L chains. Both H and L chain site-directed transgenic mice show increased B cell anergy when VprBP is inactivated in B cells. Taken together, these data argue that VprBP is required for the efficient receptor editing and selection of Igκ(+) B cells, but is largely dispensable for Igλ(+) B cell development and selection, and that VprBP is necessary to rescue autoreactive B cells from anergy induction.
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Affiliation(s)
- Victoria L Palmer
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
| | - Razia Aziz-Seible
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
| | - Michele D Kassmeier
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
| | - Mary Rothermund
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
| | - Greg A Perry
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
| | - Patrick C Swanson
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE 68178
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3
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Abstract
Follicular lymphoma (FL) pathogenesis is a complex and fascinating multi-hit process, escalating along successive derailments of the distinctive molecular and cellular mechanisms paving B-cell differentiation and activation. This progressive subversion of B-cell receptor diversification mechanisms and B-cell homeostasis likely occurs during a protracted preclinical phase of asymptomatic growth, in which premalignant clones already disseminate and establish "niches" in secondary lymphoid organs. Following FL diagnosis, a parallel indolent behavior is observed in most patients, slowly progressing over a period of many years, to eventually generate a highly refractory (and in some case transform into an aggressive subtype of) lymphoma. Novel insights in human germinal center B-cell biology recently allowed a more comprehensive understanding of the various illegitimate events sequentially involved in the premalignant progression phases. In this review, we will discuss how these new data have modified our perception of early FL pathogenesis, the new questions and challenges it opened up, and how this knowledge could impact on innovative programs of early detection, follow-up, and patient management.
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Li G, Alt FW, Cheng HL, Brush JW, Goff PH, Murphy MM, Franco S, Zhang Y, Zha S. Lymphocyte-specific compensation for XLF/cernunnos end-joining functions in V(D)J recombination. Mol Cell 2008; 31:631-40. [PMID: 18775323 PMCID: PMC2630261 DOI: 10.1016/j.molcel.2008.07.017] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2008] [Revised: 06/17/2008] [Accepted: 07/18/2008] [Indexed: 01/08/2023]
Abstract
Mutations in XLF/Cernunnos (XLF) cause lymphocytopenia in humans, and various studies suggest an XLF role in classical nonhomologous end joining (C-NHEJ). We now find that XLF-deficient mouse embryonic fibroblasts are ionizing radiation (IR) sensitive and severely impaired for ability to support V(D)J recombination. Yet mature lymphocyte numbers in XLF-deficient mice are only modestly decreased. Moreover, XLF-deficient pro-B lines, while IR-sensitive, perform V(D)J recombination at nearly wild-type levels. Correspondingly, XLF/p53-double-deficient mice are not markedly prone to the pro-B lymphomas that occur in previously characterized C-NHEJ/p53-deficient mice; however, like other C-NHEJ/p53-deficient mice, they still develop medulloblastomas. Despite nearly normal V(D)J recombination in developing B cells, XLF-deficient mature B cells are moderately defective for immunoglobulin heavy-chain class switch recombination. Together, our results implicate XLF as a C-NHEJ factor but also indicate that developing mouse lymphocytes harbor cell-type-specific factors/pathways that compensate for the absence of XLF function during V(D)J recombination.
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Affiliation(s)
- Gang Li
- Howard Hughes Medical Institute, The Children's Hospital, The CBR Institute of Biomedical Research, Harvard Medical School, Boston, MA 02115, USA
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5
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Wikström I, Bergqvist I, Holmberg D, Forssell J. Dmu expression causes enrichment of MZ B cells, but is non permissive for B cell maturation in Rag2-/- mice even if combined with Bcl-2. Mol Immunol 2005; 43:1316-24. [PMID: 16321440 DOI: 10.1016/j.molimm.2005.09.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Accepted: 09/24/2005] [Indexed: 11/17/2022]
Abstract
Rearrangements in reading frame 2 promote the expression of a truncated heavy chain, the Dmu protein. Dmu can assemble into a pre-B cell receptor like complex that appears to induce a subset of signals elicited by full length mu, but cannot promote the pro-B to pre-B cell transition of Rag-/- B cells. In order to determine if this could stem from an impaired survival signal not properly induced by the Dmu protein, we introduced Bcl-2 into Dmu-transgenic, Rag2-/- mice. Despite the fact that the Bcl-2 transgene expression promoted some increase in the fraction of CD43- B cells, an identical increase was also observed in Rag2-/- mice. Moreover, whereas in mu-transgenic Rag2-/-Bcl-2+ mice, CD2 and CD25 expression were up regulated and c-Kit was down regulated, these markers were unaltered in Dmu-transgenic Rag2-/- Bcl-2+ mice compared to Rag2-/- Bcl-2+ mice, indicating that Dmu cannot support pre-B cell maturation despite extended survival of B cell precursors by Bcl-2. In addition, we observed that in Dmu-transgenic recombination competent mice, the Dmu induced partial block is permissive for marginal zone B cell development whereas the formation of follicular B cells is severely reduced. While the Dmu protein is expressed in peripheral B cells escaping the block, only a minor fraction of Dmu is exposed to the outer cell surface.
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Affiliation(s)
- Ingela Wikström
- Institute for Medical Biosciences, Department of Medical and Clinical Genetics, Umeå University, 901 87 Umeå, Sweden
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6
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Guloglu FB, Bajor E, Smith BP, Roman CAJ. The Unique Region of Surrogate Light Chain Component λ5 Is a Heavy Chain-Specific Regulator of Precursor B Cell Receptor Signaling. THE JOURNAL OF IMMUNOLOGY 2005; 175:358-66. [PMID: 15972669 DOI: 10.4049/jimmunol.175.1.358] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Signals transduced by precursor-BCRs (pre-BCRs) composed of Ig mu heavy chains (HCs) and the surrogate L chain components lambda5 and VpreB are critical for B cell development. A conserved unique region (UR) of lambda5 was shown to activate pre-BCR complexes in transformed cells and to engage putative ligands, but its contribution to pre-B cell development is not known. It is also not clear why the lambda-like sequences in lambda5 are used to select HCs that will associate mainly with kappa L chains. In this study, we show that, in transformed and primary mouse B cell progenitors, receptors containing full-length HCs and lacking the lambda5UR were expressed at higher surface levels, but exhibited reduced activity compared with normal pre-BCRs in supporting developmental changes that accompany the progenitor to pre-B cell transition in primary cell culture systems and in the bone marrow in vivo. In contrast, deletion of the lambda5UR did not change net signaling output by the Dmu-pre-BCR, a developmentally defective receptor that exhibited impaired activity in the primary cell culture system. Moreover, the lambda-like sequences in lambda5 were more accommodating than kappa in supporting surface expression and signaling by the different HCs. These results show that the lambda5UR is important, although not essential, for surrogate L chain-dependent receptor signaling in primary cells, and furthermore may help allow discrimination of signaling competency between normal and Dmu-pre-BCRs. That the lambda-like portion of lambda5 in the absence of the UR was nondiscriminatory suggests that the lambda5UR focuses pre-BCR-dependent selection on the HC V region.
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Affiliation(s)
- F Betul Guloglu
- Department of Microbiology and Immunology, School of Graduate Studies, State University of New York, Downstate Medical Center at Brooklyn, Brooklyn, NY 11203, USA
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7
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Rahman ZSM, Manser T. B cells expressing Bcl-2 and a signaling-impaired BAFF-specific receptor fail to mature and are deficient in the formation of lymphoid follicles and germinal centers. THE JOURNAL OF IMMUNOLOGY 2004; 173:6179-88. [PMID: 15528355 DOI: 10.4049/jimmunol.173.10.6179] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The TNF family cytokine B cell-activating factor belonging to the TNF family (BAFF) (BLyS) plays a fundamental role in regulating peripheral B cell survival and homeostasis. A BAFF-specific receptor (BAFF-R; BR3) appears to mediate these functions via activation of the NF-kappaB2 pathway. Signaling by the BAFF-R is also required to sustain the germinal center (GC) reaction. Engagement of this receptor results in the induction of Bcl-2, suggesting that this antiapoptotic factor acts downstream of the BAFF-R and NF-kappaB2 pathway to promote peripheral B cell survival during primary and Ag-driven development. To test this idea, we created lines of mice coexpressing a Bcl-2 transgene and a signaling-deficient form of the BAFF-R derived from the B lymphopenic A/WySnJ strain. Surprisingly, although dramatically elevated numbers of B cells accumulate in the periphery of these mice, these B cells exhibit extremely perturbed primary development, formation of lymphoid microenvironments, and GC and IgG responses. Moreover, mice expressing the bcl-2 transgene alone display a loss of marginal zone B cells, an expansion of follicular B cells that appear immature, and alterations of the GC reaction. These results suggest that the BAFF-R and Bcl-2 regulate key and nonoverlapping aspects of peripheral B cell survival and development.
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Affiliation(s)
- Ziaur S M Rahman
- Department of Microbiology and Immunology and The Kimmel Cancer Institute, Thomas Jefferson Medical College, Philadelphia, PA 19017, USA
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8
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Milne CD, Fleming HE, Zhang Y, Paige CJ. Mechanisms of selection mediated by interleukin-7, the preBCR, and hemokinin-1 during B-cell development. Immunol Rev 2004; 197:75-88. [PMID: 14962188 DOI: 10.1111/j.0105-2896.2004.0103.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Many of the stromal-derived signals and factors that regulate B lymphopoiesis have been identified. We review recent evidence from our laboratory that shows that there are at least three phases during B-cell development when cells direct their own maturation, independent of stromal cells. Following the expression of the preB-cell receptor (preBCR), cells acquire the ability to proliferate in low levels of interleukin-7 (IL-7), which acts as a self-selecting mechanism to expand cells that have successfully expressed a preBCR in environments that are non-permissive to preBCR- cells. Second, the preBCR is required for a contact-mediated event between B-cell progenitors. Disruption at this stage prevents the further maturation of progenitors to the lipopolysaccharide (LPS)-responsive stage. Finally, the transition from IL-7 receptor to mature antigen receptor-based signaling is enhanced by a novel member of the tachykinin family, hemokinin-1. This series of maturation, survival, and differentiation signals is generated by B-lineage cells as they progress through developmental checkpoints on the way to becoming functionally mature cells.
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9
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Galler GR, Mundt C, Parker M, Pelanda R, Mårtensson IL, Winkler TH. Surface mu heavy chain signals down-regulation of the V(D)J-recombinase machinery in the absence of surrogate light chain components. ACTA ACUST UNITED AC 2004; 199:1523-32. [PMID: 15173209 PMCID: PMC2211789 DOI: 10.1084/jem.20031523] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Early B cell development is characterized by stepwise, ordered rearrangement of the immunoglobulin (Ig) heavy (HC) and light (LC) chain genes. Only one of the two alleles of these genes is used to produce a receptor, a phenomenon referred to as allelic exclusion. It has been suggested that pre–B cell receptor (pre-BCR) signals are responsible for down-regulation of the VDJH-recombinase machinery (Rag1, Rag2, and terminal deoxynucleotidyl transferase [TdT]), thereby preventing further rearrangement on the second HC allele. Using a mouse model, we show that expression of an inducible μHC transgene in Rag2−/− pro–B cells induces down-regulation of the following: (a) TdT protein, (b) a transgenic green fluorescent protein reporter reflecting endogenous Rag2 expression, and (c) Rag1 primary transcripts. Similar effects were also observed in the absence of surrogate LC (SLC) components, but not in the absence of the signaling subunit Ig-α. Furthermore, in wild-type mice and in mice lacking either λ5, VpreB1/2, or the entire SLC, the TdT protein is down-regulated in μHC+LC− pre–B cells. Surprisingly, μHC without LC is expressed on the surface of pro–/pre–B cells from λ5−/−, VpreB1−/−VpreB2−/−, and SLC−/− mice. Thus, SLC or LC is not required for μHC cell surface expression and signaling in these cells. Therefore, these findings offer an explanation for the occurrence of HC allelic exclusion in mice lacking SLC components.
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Affiliation(s)
- Gunther R Galler
- Hematopoiesis Unit, Nikolaus-Fiebiger-Center, Friedrich-Alexander University, Glueckstrasse 6, 91054 Erlangen, Germany
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10
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Fuentes-Pananá EM, Bannish G, Monroe JG. Basal B-cell receptor signaling in B lymphocytes: mechanisms of regulation and role in positive selection, differentiation, and peripheral survival. Immunol Rev 2004; 197:26-40. [PMID: 14962184 DOI: 10.1111/j.0105-2896.2004.0105.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
B-cell development is a highly ordered multistep process dependent upon signals generated by the pre-B and B-cell antigen receptor (BCR). BCR signals drive maturation of the B cell by integrating a number of parallel and sequential biological processes that result in generation of fully immunocompetent B cells. Among these biological processes are positive selection through several developmental checkpoints, negative selection of potentially self-reactive B cells, and activation of the mature B cell. In addition, recent studies have shown that developing and mature B cells rely on the constant activity of the BCR for their continued survival. Ligand (antigen)-dependent and -independent mechanisms of BCR signaling have been proposed, but their specific contributions to B-cell maturation and differentiation in the bone marrow and periphery are not completely clear. We discuss here a model, whereby ligand-independent basal BCR activity would be sufficient to trigger B-cell development through to the mature stage. However, long-term survival and formation of specific mature B-cell populations may be dependent on ligand-receptor interactions.
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Affiliation(s)
- Ezequiel M Fuentes-Pananá
- Department of Pathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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11
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Tretter T, Ross AE, Dordai DI, Desiderio S. Mimicry of pre-B cell receptor signaling by activation of the tyrosine kinase Blk. ACTA ACUST UNITED AC 2003; 198:1863-73. [PMID: 14662906 PMCID: PMC2194155 DOI: 10.1084/jem.20030729] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
During B lymphoid ontogeny, assembly of the pre–B cell receptor (BCR) is a principal developmental checkpoint at which several Src-related kinases may play redundant roles. Here the Src-related kinase Blk is shown to effect functions associated with the pre-BCR. B lymphoid expression of an active Blk mutant caused proliferation of B progenitor cells and enhanced responsiveness of these cells to interleukin 7. In mice lacking a functional pre-BCR, active Blk supported maturation beyond the pro–B cell stage, suppressed VH to DJH rearrangement, relieved selection for productive heavy chain rearrangement, and stimulated κ rearrangement. These alterations were accompanied by tyrosine phosphorylation of immunoglobulin β and Syk, as well as changes in gene expression consistent with developmental maturation. Thus, sustained activation of Blk induces responses normally associated with the pre-BCR.
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Affiliation(s)
- Theresa Tretter
- Department of Molecular Biology and Genetics, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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12
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Wen R, Chen Y, Xue L, Schuman J, Yang S, Morris SW, Wang D. Phospholipase Cgamma2 provides survival signals via Bcl2 and A1 in different subpopulations of B cells. J Biol Chem 2003; 278:43654-62. [PMID: 12928432 DOI: 10.1074/jbc.m307318200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PLCgamma2 plays a critical role in B cell receptor (BCR) signaling and its targeted deletion results in defective B cell development and function. Here, we show that PLCgamma2 deficiency specifically blocks B cell maturation at the transitional type 2 (T2) to follicular (FO) B cell transition and the PLCgamma2 pathway regulates survival of B cells. BCR-induced apoptosis is dramatically enhanced in all subsets of splenic PLCgamma2-deficient B cells, especially in T2 and FO B cell subpopulations. We also find that all splenic PLCgamma2-deficient B cell subpopulations express abnormally low levels of Bcl-2 protein. In addition, PLCgamma2 deficiency disrupts BCR-mediated induction of A1 expression. Enforced expression of Bcl-2 prevents BCR-induced apoptosis in all splenic PLCgamma2-deficient B cell subpopulations and partially restores the numbers of PLCgamma2-deficient FO B cells. In contrast to Bcl-2, enforced expression of A1 preferentially prevents BCR-induced apoptosis in PLCgamma2-deficient FO B cells and partially restores the numbers of these B cells. Therefore, the PLCgamma2 pathway provides a survival signal via regulation of Bcl-2 in all splenic B cell subpopulations and via additional induction of A1 in mature FO B cells.
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Affiliation(s)
- Renren Wen
- Blood Research Institute, the Blood Center of Southeastern Wisconsin, Milwaukee, Wisconsin 53226, USA
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13
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Abstract
Apoptotic cell death plays a critical role in the development and functioning of the immune system. During differentiation, apoptosis weeds out lymphocytes lacking useful antigen receptors and those expressing dangerous ones. Lymphocyte death is also involved in limiting the magnitude and duration of immune responses to infection. In this review, we describe the role of the Bcl-2 protein family, and to a lesser extent that of death receptors (members of the tumor necrosis factor receptor family with a death domain), in the control of lymphoid and myeloid cell survival. We also consider the pathogenic consequences of failure of apoptosis in the immune system.
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Affiliation(s)
- Vanessa S Marsden
- Molecular Genetics of Cancer Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
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14
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Abstract
The stochastic nature of rearrangement and diversification of the gene segments encoding immunoglobulins (Igs) and T cell receptors (TCRs) inevitably gives rise to immature B and T lymphocytes that lack antigen receptors or express useless or dangerous (self-antigen-specific) ones. Signaling through antigen receptors promotes survival, proliferative expansion and further differentiation of useful cells and deletion of the useless and dangerous ones. During immune responses, pathogen-specific B and T lymphocytes, as well as cells of the innate immune system, undergo extensive proliferation and develop effector functions, such as antibody secretion, cytotoxicity or cytokine production. To prevent tissue damage by these effector molecules, activated lymphocytes are removed when an infection has been overcome. Together with other mechanisms, including developmental arrest and induction of unresponsiveness (anergy), programmed cell death (apoptosis) of autoreactive lymphocytes safeguards immunological tolerance to self and assists in the development of an effective immune system. We have been investigating the molecular mechanisms that control programmed cell death. This review describes some of our experiments using transgenic and knockout mice, which overexpress or lack apoptosis regulators, that led to discoveries on how life and death decisions are made during development and functioning of the immune system.
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Affiliation(s)
- Andreas Strasser
- Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, PO Royal Melbourne Hospital, Victoria, Australia.
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15
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Mathieu N, Spicuglia S, Gorbatch S, Cabaud O, Fernex C, Verthuy C, Hempel WM, Hueber AO, Ferrier P. Assessing the role of the T cell receptor beta gene enhancer in regulating coding joint formation during V(D)J recombination. J Biol Chem 2003; 278:18101-9. [PMID: 12639959 DOI: 10.1074/jbc.m212647200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To assess the role of the T cell receptor (TCR) beta gene enhancer (Ebeta) in regulating the processing of VDJ recombinase-generated coding ends, we assayed TCRbeta rearrangement of Ebeta-deleted (DeltaEbeta) thymocytes in which cell death is inhibited via expression of a Bcl-2 transgene. Compared with DeltaEbeta, DeltaEbeta Bcl-2 thymocytes show a small accumulation of TCRbeta standard recombination products, including coding ends, that involves the proximal Dbeta-Jbeta and Vbeta14 loci but not the distal 5' Vbeta genes. These effects are detectable in double negative pro-T cells, predominate in double positive pre-T cells, and correlate with regional changes in chromosomal structure during double negative-to-double positive differentiation. We propose that Ebeta, by driving long range nucleoprotein interactions and the control of locus expression and chromatin structure, indirectly contributes to the stabilization of coding ends within the recombination processing complexes. The results also illustrate Ebeta-dependent and -independent changes in chromosomal structure, suggesting distinct modes of regulation of TCRbeta allelic exclusion depending on the position within the locus.
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Affiliation(s)
- Noëlle Mathieu
- Centre d'Immunologie de Marseille-Luminy, INSERM, CNRS, Université de la Méditerranée, 13288 Marseille, France
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16
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Zou X, Piper TA, Smith JA, Allen ND, Xian J, Brüggemann M. Block in development at the pre-B-II to immature B cell stage in mice without Ig kappa and Ig lambda light chain. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:1354-61. [PMID: 12538695 DOI: 10.4049/jimmunol.170.3.1354] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Silencing individual C (constant region) lambda genes in a kappa(-/-) background reduces mature B cell levels, and L chain-deficient (lambda(-/-)kappa(-/-)) mice attain a complete block in B cell development at the stage when L chain rearrangement, resulting in surface IgM expression, should be completed. L chain deficiency prevents B cell receptor association, and L chain function cannot be substituted (e.g., by surrogate L chain). Nevertheless, precursor cell levels, controlled by developmental progression and checkpoint apoptosis, are maintained, and B cell development in the bone marrow is fully retained up to the immature stage. L chain deficiency allows H chain retention in the cytoplasm, but prevents H chain release from the cell, and as a result secondary lymphoid organs are B cell depleted while T cell levels remain normal.
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Affiliation(s)
- Xiangang Zou
- Laboratory of Developmental Immunology, The Babraham Institute, Babraham, Cambridge, United Kingdom
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17
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Yamanaka T, Helgeland L, Farstad IN, Fukushima H, Midtvedt T, Brandtzaeg P. Microbial colonization drives lymphocyte accumulation and differentiation in the follicle-associated epithelium of Peyer's patches. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 170:816-22. [PMID: 12517945 DOI: 10.4049/jimmunol.170.2.816] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Peyer's patches (PPs) are lined by follicle-associated epithelium (FAE) with Ag-transporting M cells. To investigate the spatial relationships of B cells, T cells, and dendritic cells (DCs) in PPs during microbial colonization, their in situ redistribution was examined in germfree (GF) rats exposed to a conventional pathogen-free microflora (conventionalized, CV). Although occasional B and T cells occurred in the FAE of GF rats, it contained mainly immature DCs (CD4(+)CD86(-)), whereas mature DCs (CD86(high)) were seen in the interfollicular zones even under GF conditions. In CV rats, DCs had disappeared from the FAE, which instead contained clusters by B and T cells associated with induction of putative M cell pockets. CD86 was seen neither in the FAE nor in the follicles under GF conditions, but it became apparent on intraepithelial B cells 5 wk after colonization. The level of CD86 on these B cells was comparable to that on germinal center B cells, although the B cell follicles did not show direct contact with the M cell areas. B cells in the follicular mantles acquired Bcl-2 after 12 wk in CV rats, whereas B cells in the FAE did not express Bcl-2 at a substantial level throughout the experimental period. The cellular redistribution patterns and phenotypic characteristics observed after colonization suggested that immature DCs, but not B cells, are involved in Ag presentation during primary immune responses against intestinal bacteria. However, the spatial cellular relationships sequentially being established among DCs, B cells, and T cells in PPs, are most likely important for the induction of post-germinal center B cells subsequently residing within the M cell pockets.
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Affiliation(s)
- Takeshi Yamanaka
- Laboratory for Immunohistochemistry and Immunopathology, Institute of Pathology, University of Oslo, Rikshospitalet, Norway
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18
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Meffre E, Nussenzweig MC. Deletion of immunoglobulin beta in developing B cells leads to cell death. Proc Natl Acad Sci U S A 2002; 99:11334-9. [PMID: 12165571 PMCID: PMC123257 DOI: 10.1073/pnas.172369999] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2002] [Accepted: 06/20/2002] [Indexed: 01/25/2023] Open
Abstract
Inducible gene-targeting experiments have shown that Igmu expression is essential for maintaining survival of mature B cells, but the role of Igmu expression in immature B cell survival has not been determined. To assess whether continued B cell receptor (BCR) expression is required for bone marrow B cell precursor development and survival, we developed a method for conditional gene deletion in these cells. Recombination-activating gene regulatory elements were used to express Igbeta cDNA as a transgene to complement Igbeta(-/-) mice. Transgenic Igbeta expression was found in proB and small preB cells and was extinguished in large preB and immature B cells. Igbeta deletion from large preB cells and immature B cells resulted in cell death that could be rescued by transgenic bcl-2 expression. However, transgenic bcl-2 expression was unable to restore B cell development in the absence of Igbeta. We conclude that Igbeta expression is essential to maintain preB cell and immature B cell survival and to mediate B cell differentiation. In addition, complementation of null mutations with cDNAs under the control of heterologous bacterial artificial chromosomes is a useful method for cell-type-specific and developmentally regulated gene ablation in vivo.
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Affiliation(s)
- Eric Meffre
- Laboratory of Molecular Immunology, The Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10021-6399, USA
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Chuang PI, Morefield S, Liu CY, Chen S, Harlan JM, Willerford DM. Perturbation of B-cell development in mice overexpressing the Bcl-2 homolog A1. Blood 2002; 99:3350-9. [PMID: 11964303 DOI: 10.1182/blood.v99.9.3350] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Decisions about cell survival or death are central components of adaptive immunity and occur at several levels in immune system development and function. The Bcl-2 family of homologous proteins plays an important role in these decisions in lymphoid cells. Bcl-2, Bcl-xL, and A1 are differentially expressed during B- and T-cell development, and they have shared and distinct roles in regulating cell death. We sought to gain insight into the role of A1 in immune system development and function. A murine A1-a transgene was expressed under the control of the Emu enhancer, and mice with A1 overexpression in B- and T-cell lineages were derived. Thymocytes and early B cells in Emu-A1 mice showed extended survival. B-lineage development was altered, with expansion of the pro-B cell subset at the expense of pre-B cells, suggesting an impairment of the pro- to pre-B-cell transition. This early B-cell phenotype resembled Emu-Bcl-xL mice but did not preferentially rescue cells with completed V(D)J rearrangements of the immunoglobulin heavy chain. In contrast to Emu-Bcl-2 transgenes, A1 expression in pro-B cells did not rescue pre-B-cell development in SCID mice. These studies indicate that A1 protects lymphocytes from apoptosis in vitro but that it has lineage- and stage-specific effects on lymphoid development. Comparison with the effects of Bcl-2 and Bcl-xL expressed under similar control elements supports the model that antiapoptotic Bcl-2 homologs interact differentially with intracellular pathways affecting development and apoptosis in lymphoid cells.
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Affiliation(s)
- Peter I Chuang
- Department of Medicine, University of Washington, Seattle 98195, USA
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20
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Malynn BA, Shaw AC, Young F, Stewart V, Alt FW. Truncated immunoglobulin Dmu causes incomplete developmental progression of RAG-deficient pro-B cells. Mol Immunol 2002; 38:547-56. [PMID: 11750656 DOI: 10.1016/s0161-5890(01)00085-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Early stages of B cell development are dependent on the expression of a pre-B cell receptor (BCR), composed of a mu heavy chain (HC) in association with surrogate light chain (SLC) proteins and the signaling molecules, Igalpha and Igbeta. During the formation of the variable region of the mu chain by somatic gene rearrangement, a truncated form of the mu protein (called Dmu) is sometimes produced by the rearrangement of a D(H) segment to a J(H) segment using one of three reading frames (designated rf2). When a Dmu protein is formed, subsequent B cell development is blocked by down-regulation of further HC rearrangements, so that a full-length muHC cannot be formed. In this study, we demonstrate that in recombinase activating gene (RAG)-2-deficient B220(+) CD43(+) pro-B cells in which B lymphopoiesis has been arrested at fraction C, transgenic expression of Dmu promoted partial developmental progression to fraction C', but was unable to mediate the pro-B to pre-B cell transition to fraction D effected by full-length muHC protein. These data suggest that the intracellular signaling pathways engaged by the Dmu pre-BCR are insufficient to facilitate the expansion and/or survival of pre-B cells, and are distinct from those engaged by the pre-BCR-containing full-length muHC.
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Affiliation(s)
- Barbara A Malynn
- The Center for Blood Research, Harvard Medical School, Boston, MA 02115, USA
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21
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Merchant M, Longnecker R. LMP2A survival and developmental signals are transmitted through Btk-dependent and Btk-independent pathways. Virology 2001; 291:46-54. [PMID: 11878875 DOI: 10.1006/viro.2001.1187] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The latent membrane protein 2A (LMP2A) of Epstein--Barr virus (EBV) has been implicated in controlling viral latency due to the ability of LMP2A to block B cell antigen receptor (BCR) signaling in vitro and to alter B cell development and enhance B cell survival in vivo. These LMP2A functions require interactions with the protein tyrosine kinases Syk and Lyn. However, a role for the Bruton's tyrosine kinase (Btk) has not been investigated for these LMP2A functions. To investigate whether Btk is important for LMP2A developmental and survival signals in vivo, LMP2A transgenic animals were mated to Btk deficient (Btk(-/-)) mice. Unlike LMP2A(+), Btk(+/+) transgenic littermate controls, LMP2A(+), Btk(-/-) animals do not generate immunoglobulin (Ig) receptorless B cells in the periphery and instead produce Ig(+) B cells similar to those in the Btk(-/-) mice. Interestingly, however, LMP2A(+), Btk(-/-) animals produce B cells at a vastly reduced level compared to Btk(-/-) littermates, indicating that LMP2A affects B cell development in the absence of Btk. In the RAG-1(-/-), Btk(-/-) double knockout background, LMP2A is still capable of enhancing the survival of Ig-receptorless B cells. Use of Btk phosphopeptide-specific antibodies reveals that Btk is constitutively phosphorylated in LMP2A-expressing cell lines. These data indicate that LMP2A initiates both Btk-dependent and Btk-independent pathways, resulting in altered B cell development and enhanced B cell survival.
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Affiliation(s)
- M Merchant
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA
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22
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Fleming HE, Paige CJ. Pre-B cell receptor signaling mediates selective response to IL-7 at the pro-B to pre-B cell transition via an ERK/MAP kinase-dependent pathway. Immunity 2001; 15:521-31. [PMID: 11672535 DOI: 10.1016/s1074-7613(01)00216-3] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
B lymphocyte development is regulated at multiple checkpoints, mediated by signals originating both inside and outside the cell. Two signaling pathways known to be essential in this process are interleukin-7 (IL-7) and the pre-B cell receptor (pBCR). We have shown previously that these signaling pathways intersect functionally. Specifically, response to low concentrations of IL-7 requires pBCR expression. In this report, we identify the ERK/MAP kinase pathway as a key regulatory component of this response. We propose a molecular mechanism for the selective expansion of pBCR(+) precursors and for the culling of inappropriately rearranged pro-B cells.
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Affiliation(s)
- H E Fleming
- Ontario Cancer Institute, Princess Margaret Hospital, University Health Network, Departments of Immunology and Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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23
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24
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Affiliation(s)
- K Newton
- Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
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25
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Ruetsch NR, Bosma GC, Bosma MJ. Unexpected rearrangement and expression of the immunoglobulin lambda1 locus in scid mice. J Exp Med 2000; 191:1933-43. [PMID: 10839808 PMCID: PMC2213526 DOI: 10.1084/jem.191.11.1933] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2000] [Accepted: 04/07/2000] [Indexed: 11/25/2022] Open
Abstract
In severe combined immunodeficient (scid) mice, V(D)J recombination is severely impaired due to a recessive mutation (scid). Thus, we were surprised to find in this study that Vlambda1-Jlambda1 rearrangement is routinely detectable in scid fetal liver, adult bone marrow, and spleen in the apparent absence of completed VH-DJH and Vkappa-Jkappa rearrangements. Particularly surprising, we found the level of Vlambda1-Jlambda1 rearrangement in scid fetal liver to be comparable to that in fetal liver of wild-type mice. The majority of scid Vlambda1-Jlambda1 rearrangements contained abnormal deletions at the VJ junction, consistent with the known effect of scid. However, approximately 15% of Vlambda1-Jlambda1 rearrangements lacked abnormal deletions. Productive lambda1 transcripts resulting from in-frame rearrangements were readily detectable in scid adult bone marrow and spleen, consistent with our ability to detect lambda1-expressing cells by flow cytometry in the spleens of bcl-2-transgenic scid mice. Strikingly, lambda1 transcripts from individual scid mice often showed VJ junctional sequences with the same recurring palindromic (P) additions of three, four, or five nucleotides. To account for these findings, we suggest that (a) nonhomologous end joining of Vlambda1 and Jlambda1 coding ends in fetal B lineage cells may not be (severely) impaired by scid; (b) recurring P additions in scid lambda1 transcripts may reflect certain molecular constraints imposed by scid on the resolution of Vlambda1 and Jlambda1 hairpin coding ends; and (c), scid lymphocytes with productively rearranged Vlambda1 and Jlambda1 elements may differentiate into recombinase-inactive cells and emigrate from bone marrow to spleen.
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Affiliation(s)
- Norman R. Ruetsch
- Fox Chase Cancer Center, Institute for Cancer Research, Philadelphia, Pennsylvania 19111
| | - Gayle C. Bosma
- Fox Chase Cancer Center, Institute for Cancer Research, Philadelphia, Pennsylvania 19111
| | - Melvin J. Bosma
- Fox Chase Cancer Center, Institute for Cancer Research, Philadelphia, Pennsylvania 19111
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26
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Smith KG, Light A, O'Reilly LA, Ang SM, Strasser A, Tarlinton D. bcl-2 transgene expression inhibits apoptosis in the germinal center and reveals differences in the selection of memory B cells and bone marrow antibody-forming cells. J Exp Med 2000; 191:475-84. [PMID: 10662793 PMCID: PMC2195819 DOI: 10.1084/jem.191.3.475] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Immunization with T cell-dependent antigens generates long-lived memory B cells and antibody-forming cells (AFCs). Both populations originate in germinal centers and, predominantly, produce antibodies with high affinity for antigen. The means by which germinal center B cells are recruited into these populations remains unclear. We have examined affinity maturation of antigen-specific B cells in mice expressing the cell death inhibitor bcl-2 as a transgene. Such mice had reduced apoptosis in germinal centers and an excessive number of memory B cells with a low frequency of V gene somatic mutation, including those mutations encoding amino acid exchanges known to enhance affinity. Despite the frequency of AFCs being increased in bcl-2-transgenic mice, the fraction secreting high-affinity antibody in the bone marrow at day 42 remained unchanged compared with controls. The inability of BCL-2 to alter selection of bone marrow AFCs is consistent with these cells being selected within the germinal center on the basis of their affinity being above some threshold rather than their survival being due to a selective competition for an antigen-based signal. Continuous competition for antigen does, however, explain formation of the memory compartment.
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Affiliation(s)
- Kenneth G.C. Smith
- Cambridge Institute for Medical Research and the Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge CB2 2QQ, United Kingdom
| | - Amanda Light
- The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia
| | - Lorraine A. O'Reilly
- The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia
| | - Soon-Meng Ang
- The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia
| | - Andreas Strasser
- The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia
| | - David Tarlinton
- The Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria 3050, Australia
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27
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Nemazee D, Kouskoff V, Hertz M, Lang J, Melamed D, Pape K, Retter M. B-cell-receptor-dependent positive and negative selection in immature B cells. Curr Top Microbiol Immunol 1999; 245:57-71. [PMID: 10533318 DOI: 10.1007/978-3-642-59641-4_3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review touches on only a small part of the complex biology of B cells, but serves to illustrate the point that the antigen receptor is the most important of many cell-surface receptors affecting cell-fate decisions. Receptor expression is necessary, but not sufficient, for cell survival. It is also essential that a B cell's antigen-receptor specificity be appropriate for its environment. The need to balance reactivity with self tolerance has resulted in an intricate feedback control (affected by both the recombinase and cell survival) that regulates independent selection events at the level of the receptor and the cell.
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Affiliation(s)
- D Nemazee
- Scripps Research Institute, La Jolla, CA 92037, USA
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28
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Monroe RJ, Seidl KJ, Gaertner F, Han S, Chen F, Sekiguchi J, Wang J, Ferrini R, Davidson L, Kelsoe G, Alt FW. RAG2:GFP knockin mice reveal novel aspects of RAG2 expression in primary and peripheral lymphoid tissues. Immunity 1999; 11:201-12. [PMID: 10485655 DOI: 10.1016/s1074-7613(00)80095-3] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We generated mice in which a functional RAG2:GFP fusion gene is knocked in to the endogenous RAG2 locus. In bone marrow and thymus, RAG2:GFP expression occurs in appropriate stages of developing B and T cells as well as in immature bone marrow IgM+ B cells. RAG2:GFP also is expressed in IgD+ B cells following cross-linking of IgM on immature IgM+ IgD+ B cells generated in vitro. RAG2:GFP expression is undetectable in most immature splenic B cells; however, in young RAG2:GFP mice, there are substantial numbers of splenic RAG2:GFP+ cells that mostly resemble pre-B cells. The latter population decreases in size with age but reappears following immunization of older RAG2:GFP mice. We discuss the implications of these findings for current models of receptor assembly and diversification.
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Affiliation(s)
- R J Monroe
- Howard Hughes Medical Institute, The Children's Hospital, The Center for Blood Research and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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29
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Malissen B, Ardouin L, Lin SY, Gillet A, Malissen M. Function of the CD3 subunits of the pre-TCR and TCR complexes during T cell development. Adv Immunol 1999; 72:103-48. [PMID: 10361573 DOI: 10.1016/s0065-2776(08)60018-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- B Malissen
- Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, France
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30
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Shaw AC, Swat W, Davidson L, Alt FW. Induction of Ig light chain gene rearrangement in heavy chain-deficient B cells by activated Ras. Proc Natl Acad Sci U S A 1999; 96:2239-43. [PMID: 10051625 PMCID: PMC26767 DOI: 10.1073/pnas.96.5.2239] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During B cell development, rearrangement and expression of Ig heavy chain (HC) genes promote development and expansion of pre-B cells accompanied by the onset of Ig light chain (LC) variable region gene assembly. To elucidate the signaling pathways that control these events, we have tested the ability of activated Ras expression to promote B cell differentiation to the stage of LC gene rearrangement in the absence of Ig HC gene expression. For this purpose, we introduced an activated Ras expression construct into JH-deleted embryonic stem cells that lack the ability to assemble HC variable region genes and assayed differentiation potential by recombination activating gene (RAG) 2-deficient blastocyst complementation. We found that activated Ras expression induces the progression of B lineage cells beyond the developmental checkpoint ordinarily controlled by mu HC. Such Ras/JH-deleted B cells accumulate in the periphery but continue to express markers associated with precursor B cells including RAG gene products. These peripheral Ras/JH-deleted B cell populations show extensive Ig LC gene rearrangement but maintain an extent of kappa LC gene rearrangement and a preference for kappa over lambda LC gene rearrangement similar to that of wild-type B cells. We discuss these findings in the context of potential mechanisms that may regulate Ig LC gene rearrangement.
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Affiliation(s)
- A C Shaw
- Howard Hughes Medical Institute, Boston, MA 02115, USA.
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31
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Lu L, Chaudhury P, Osmond DG. Regulation of Cell Survival During B Lymphopoiesis: Apoptosis and Bcl-2/Bax Content of Precursor B Cells in Bone Marrow of Mice with Altered Expression of IL-7 and Recombinase-Activating Gene-2. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.4.1931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
B cell development in mouse bone marrow depends critically upon IL-7. To examine the possible in vivo trophic role of IL-7, we have quantitated apoptosis and Bcl-2 family proteins in populations of phenotypically defined B lineage cells in IL-7-deficient and IL-7-overexpressing mice. Using immunofluorescence labeling, multiparameter flow cytometry, and a short-term culture assay, we show that the apoptotic rates of precursor B cells, but not of more mature B cells, are enhanced by IL-7 gene deletion, associated with increased intracellular content of Bax and decreased Bcl-2, while, conversely, an IL-7 transgene suppresses precursor B cell apoptosis and produces low Bax and high Bcl-2 levels. During normal B cell development, high Bax/Bcl-2 ratios characterize cells undergoing greatest apoptotic cell death. Pro-B cells in RAG-2−/− mice, all destined to abort, show elevated Bax levels and Bax/Bcl-2 ratios. By comparison with the elevated rate of pro-B cell apoptosis in RAG-2−/− mice, provisional estimates have been made for the fraction of pro-B cells undergoing apoptosis in normal mice (70%), IL-7−/− mice (85%), and IL-7 transgenic mice (35%). The results demonstrate that IL-7 strongly promotes in vivo cell survival and maintains antiapoptotic Bcl-2/Bax ratios during the development of precursor B cells in mouse bone marrow.
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Affiliation(s)
- Liwei Lu
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
| | - Prosanto Chaudhury
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
| | - Dennis G. Osmond
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
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32
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Affiliation(s)
- L O'Connor
- Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Australia
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33
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Shaw AC, Swat W, Ferrini R, Davidson L, Alt FW. Activated Ras signals developmental progression of recombinase-activating gene (RAG)-deficient pro-B lymphocytes. J Exp Med 1999; 189:123-9. [PMID: 9874569 PMCID: PMC1887686 DOI: 10.1084/jem.189.1.123] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/1998] [Revised: 10/27/1998] [Indexed: 02/04/2023] Open
Abstract
To elucidate the intracellular pathways that mediate early B cell development, we directed expression of activated Ras to the B cell lineage in the context of the recombination-activating gene 1 (RAG1)-deficient background (referred to as Ras-RAG). Similar to the effects of an immunoglobulin (Ig) mu heavy chain (HC) transgene, activated Ras caused progression of RAG1-deficient progenitor (pro)-B cells to cells that shared many characteristics with precursor (pre)-B cells, including downregulation of surface CD43 expression plus expression of lambda5, RAG2, and germline kappa locus transcripts. However, these Ras-RAG pre-B cells also upregulated surface markers characteristic of more mature B cell stages and populated peripheral lymphoid tissues, with an overall phenotype reminiscent of B lineage cells generated in a RAG- deficient background as a result of expression of an Ig mu HC together with a Bcl-2 transgene. Taken together, these findings suggest that activated Ras signaling in pro-B cells induces developmental progression by activating both differentiation and survival signals.
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Affiliation(s)
- A C Shaw
- Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
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34
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Thévenin C, Nutt SL, Busslinger M. Early function of Pax5 (BSAP) before the pre-B cell receptor stage of B lymphopoiesis. J Exp Med 1998; 188:735-44. [PMID: 9705955 PMCID: PMC2213350 DOI: 10.1084/jem.188.4.735] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The formation of the pre-B cell receptor (BCR) corresponds to an important checkpoint in B cell development that selects pro-B (pre-BI) cells expressing a functionally rearranged immunoglobulin mu (Igmu) heavy chain protein to undergo the transition to the pre-B (pre-BII) cell stage. The pre-BCR contains, in addition to Igmu, the surrogate light chains lambda5 and VpreB and the signal transducing proteins Igalpha and Igbeta. The absence of one of these pre-BCR components is known to arrest B cell development at the pre-BI cell stage. Disruption of the Pax5 gene, which codes for the B cell-specific activator protein (BSAP), also blocks adult B lymphopoiesis at the pre-BI cell stage. Moreover, expression of the mb-1 (Igalpha) gene and VH-to-DHJH recombination at the IgH locus are reduced in Pax5-deficient B lymphocytes approximately 10- and approximately 50-fold, respectively. Here we demonstrate that complementation of these deficiencies in pre-BCR components by expression of functionally rearranged Ig mu and chimeric Igmu-Igbeta transgenes fails to advance B cell development to the pre-BII cell stage in Pax5 (-/-) mice in contrast to RAG2 (-/-) mice. Furthermore, the pre-BCR is stably expressed on cultured pre-BI cells from Igmu transgenic, Pax5-deficient bone marrow, but is unable to elicit its normal signaling responses. In addition, the early developmental block is unlikely to be caused by the absence of a survival signal, as it could not be rescued by expression of a bcl2 transgene in Pax5-deficient pre-BI cells. Together, these data demonstrate that the absence of Pax5 arrests adult B lymphopoiesis at an early developmental stage that is unresponsive to pre-BCR signaling.
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Affiliation(s)
- C Thévenin
- Research Institute of Molecular Pathology, A-1030 Vienna, Austria
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35
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Wang YH, Nomura J, Faye-Petersen OM, Cooper MD. Surrogate Light Chain Production During B Cell Differentiation: Differential Intracellular Versus Cell Surface Expression. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.3.1132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
Expression of the surrogate light (ψL) chain genes encoding the VpreB and λ5/14.1 proteins is restricted to B-lineage cells. Pro-B and pre-B cells produce ψL chains, but whether both employ these as cell surface receptor components remains enigmatic. Recombinant human VpreB protein was used to generate a large panel of monoclonal anti-VpreB Abs to examine this issue. Native ψL chain proteins within pro-B cells as well as those serving as receptor components on pre-B cells were precipitated by 16 of the 26 anti-VpreB Abs. Surrogate light chains were easily detected on pre-B cell lines, whereas these anti-VpreB Abs reacted with pro-B cell lines only after plasma membrane permeabilization. The subpopulation of normal bone marrow cells bearing pre-B receptors included large and small pre-B cells exclusively, although pro-B cells also contained intracellular VpreB. VpreB proteins were not detected on or within B cells in bone marrow or the circulation, but a subpopulation of B cells in germinal centers was found to express the VpreB proteins intracellularly. Surrogate L chains are thus intermittently produced during human B-lineage differentiation, while their role as receptor components appears limited to the pre-B cell stage.
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Affiliation(s)
- Yui-Hsi Wang
- *Division of Developmental and Clinical Immunology; Departments of Medicine, Pediatrics, Microbiology, and
| | - Jun Nomura
- *Division of Developmental and Clinical Immunology; Departments of Medicine, Pediatrics, Microbiology, and
- ‡Howard Hughes Medical Institute, University of Alabama, Birmingham, AL 35924
| | | | - Max D. Cooper
- *Division of Developmental and Clinical Immunology; Departments of Medicine, Pediatrics, Microbiology, and
- †Pathology; and
- ‡Howard Hughes Medical Institute, University of Alabama, Birmingham, AL 35924
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36
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Abstract
An expanding family of BCL-2 related proteins share homology, clustered within four conserved regions, namely BCL-2 homology (BH1-4) domains, which control the ability of these proteins to dimerize and function as regulators of apoptosis. Moreover, BCL-XL, BCL-2, and BAX can form ion-conductive pores in artificial membranes. The BCL-2 family, comprised of both pro-apoptotic and anti-apoptotic members, acts as a checkpoint upstream of CASPASES and mitochondrial dysfunction. BID and BAD possess the minimal death domain BH3, and the phosphorylation of BAD connects proximal survival signals to the BCL-2 family. BCL-2 and BCL-XL display a reciprocal pattern of expression during lymphocyte development. Gain- and loss-of-function models revealed stage-specific roles for BCL-2 and BCL-XL. BCL-2 can rescue maturation at several points of lymphocyte development. The BCL-2 family also reveals evidence for a cell-autonomous coordination between the opposing pathways of proliferation and cell death.
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Affiliation(s)
- D T Chao
- Howard Hughes Medical Institute, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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37
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Martin F, Won WJ, Kearney JF. Generation of the Germline Peripheral B Cell Repertoire: VH81X-λ B Cells Are Unable to Complete All Developmental Programs. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.160.8.3748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
The generation of VH81X heavy chain λ-light chain-expressing B cells (VH81X-λ+ B cells) was studied in VH81X heavy chain transgenic mice as well as in VH81X JH −/− and VH81X JH −/− Ck −/− mice, in which competition resulting from expression of heavy and light chains from the endogenous heavy and κ light chain loci was prevented. We show that although λ light chain gene rearrangements occur normally and give rise to light chains that associate with the transgenic heavy chain to form surface and soluble IgM molecules, further B cell development is almost totally blocked. The few VH81X-λ+ B cells that are generated progress into a mature compartment (expressing surface CD21, CD22, CD23, and low CD24 and having a relatively long life span) but they also have reduced levels of surface Ig receptor and express higher amounts of Fas Ag than VH81X-κ+ B cells. These VH81X-λ+ B cells reach the peripheral lymphoid organs and accumulate in the periarteriolar lymphoid sheath but are unable to generate primary B cell follicles. In other heavy chain transgenic mice (MD2, M167, and M54), λ+ B cells are generated. However, they seem to be preferentially selected in the peripheral repertoire of some transgenic heavy chain mice (M54) but not in others (MD2, M167). These studies show that a crucial selection step is necessary for B cell survival and maintenance in which B cells, similar to T cells, receive signals depending on their clonal receptors.
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Affiliation(s)
- Flavius Martin
- Division of Developmental and Clinical Immunology, Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35394
| | - Woong-Jai Won
- Division of Developmental and Clinical Immunology, Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35394
| | - John F. Kearney
- Division of Developmental and Clinical Immunology, Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35394
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38
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Abstract
Functional immunoglobulin gene rearrangement is a sine qua non for successful B cell development in mammalian bone marrow, but other factors are also important. Studies reported during the past year have contributed new insight into the surface receptor complexes and signaling outcomes that influence the fate of B cell precursors. Identification and characterization of secreted and membrane-associated stromal cell products, and their actions on B-cell precursors, was a parallel area of ongoing investigation.
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Affiliation(s)
- T W LeBien
- Department of Laboratory Medicine/Pathology, University of Minnesota Cancer Center, Minneapolis 55455, USA.
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39
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Abstract
Members of the Bcl-2 protein family fall into two categories on the basis of their ability to either promote or suppress apoptosis. Recent findings have linked these proteins to caspases, the cysteine proteases that effect the collapse of the cell via binding to CED-4. It seems that Bcl-2 proteins influence cell survival by regulating the activation of key caspases.
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Affiliation(s)
- K Newton
- Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia
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40
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Lang J, Arnold B, Hammerling G, Harris AW, Korsmeyer S, Russell D, Strasser A, Nemazee D. Enforced Bcl-2 expression inhibits antigen-mediated clonal elimination of peripheral B cells in an antigen dose-dependent manner and promotes receptor editing in autoreactive, immature B cells. J Exp Med 1997; 186:1513-22. [PMID: 9348309 PMCID: PMC2199120 DOI: 10.1084/jem.186.9.1513] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The mechanisms that establish immune tolerance in immature and mature B cells appear to be distinct. Membrane-bound autoantigen is thought to induce developmental arrest and receptor editing in immature B cells, whereas mature B cells have shortened lifespans when exposed to the same stimulus. In this study, we used Emu-bcl-2-22 transgenic (Tg) mice to test the prediction that enforced expression of the Bcl-2 apoptotic inhibitor in B cells would rescue mature, but not immature, B cells from tolerance induction. To monitor tolerance to the natural membrane autoantigen H-2Kb, we bred 3-83mudelta (anti-Kk,b) Ig Tg mice to H-2(b) mice or to mice expressing transgene-driven Kb in the periphery. In 3-83mudelta/bcl-2 Tg mice, deletion of autoreactive B cells induced by peripheral Kb antigen expression in the liver (MT-Kb Tg) or epithelia (KerIV-Kb Tg), was partly or completely inhibited, respectively. Furthermore, Bcl-2 protected peritoneal B-2 B cells from deletion mediated by acute antigen exposure, but this protection could be overcome by higher antigen dose. In contrast to its ability to block peripheral self-tolerance, Bcl-2 overexpression failed to inhibit central tolerance induced by bone marrow antigen expression, but instead, enhanced the receptor editing process. These studies indicate that apoptosis plays distinct roles in central and peripheral B cell tolerance.
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MESH Headings
- Animals
- Antibodies, Anti-Idiotypic/analysis
- B-Lymphocyte Subsets/classification
- B-Lymphocyte Subsets/immunology
- B-Lymphocyte Subsets/metabolism
- Cell Differentiation/immunology
- Cell Survival/immunology
- Clonal Deletion
- Dose-Response Relationship, Immunologic
- Epithelial Cells/immunology
- Gene Rearrangement, B-Lymphocyte, Light Chain
- H-2 Antigens/administration & dosage
- Hybridomas/transplantation
- Immunoglobulin M/analysis
- Immunoglobulin kappa-Chains/genetics
- Immunoglobulin lambda-Chains/genetics
- Injections, Intraperitoneal
- Leukocyte Common Antigens/analysis
- Liver/cytology
- Liver/immunology
- Lymphocyte Count
- Lymphoid Tissue/cytology
- Mice
- Mice, Inbred A
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Proto-Oncogene Proteins c-bcl-2/biosynthesis
- Proto-Oncogene Proteins c-bcl-2/physiology
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Affiliation(s)
- J Lang
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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41
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Levy Y, Benlagha K, Buzyn A, Colombel M, Brouet JC, Lassoued K. IL-7 sensitizes human pre-B cells but not pro-B cells to Fas/APO-1 (CD95)-mediated apoptosis. Clin Exp Immunol 1997; 110:329-35. [PMID: 9367421 PMCID: PMC2265507 DOI: 10.1111/j.1365-2249.1997.tb08336.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Homeostasis of human B cell development is maintained by a complex network of cytoplasmic and surface expressed molecules. Abnormalities in this process may result in the expansion of malignant B cell precursors in B lineage acute lymphoblastic leukaemia (ALL). ALL cells share surface antigens with normal early precursor B cells. We have studied here the role of Fas/APO-1 (CD95) antigen on leukaemic precursor B cell line growth and survival, and the modulation of its effects by signals involved in normal early B cell development. Four ALL cell lines representative of the early steps of B cell differentiation are shown to express surface Fas/APO-1 (CD95) antigen and to undergo apoptosis in the presence of anti-Fas cross-linking antibodies. This effect is strongly enhanced when pre-B, but not pro-B cells, are pretreated with IL-7 but not with IL-2, IL-3, IL-4 or IL-10. Furthermore, pre-B cell death induced by anti-Fas antibodies in combination with IL-7 is increased upon pre-B receptor but not CD19 cross-linking. Bcl-2 and Bax protein expression is not influenced by IL-7 or pre-BR stimulation in either pro-B or pre-B cell lines. These results indicate that signals involved in normal early B cell development can modulate the Fas (CD95)-mediated apoptosis of leukaemic precursor B cells.
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Affiliation(s)
- Y Levy
- Département d'Immunologie, Hôpital Henri Mondor, Creteil, France
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42
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Nagata K, Nakamura T, Kitamura F, Kuramochi S, Taki S, Campbell KS, Karasuyama H. The Ig alpha/Igbeta heterodimer on mu-negative proB cells is competent for transducing signals to induce early B cell differentiation. Immunity 1997; 7:559-70. [PMID: 9354476 DOI: 10.1016/s1074-7613(00)80377-5] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The immunoglobulin alpha (Ig alpha)/Ig beta heterodimer was detected on the surface of mu-negative proB cell lines in association with calnexin. The cross-linking of Ig beta on proB cells freshly isolated from bone marrow of recombination activating gene (RAG)-2-deficient mice induced a rapid and transient tyrosine-phosphorylation of Ig alpha as well as an array of intracellular proteins including Syk, PI3-kinase, Vav, and SLP-76. It also elicited the phosphorylation and activation of a MAP kinase ERK but not JNK/SAPK or p38. When RAG-2-deficient mice were treated with anti-Ig beta monoclonal antibody, developmentally arrested proB cells were induced to differentiate to the small preB cell stage as observed when the mu transgene was expressed in RAG-2-deficient mice. Thus, the cross-linking of Ig beta on proB cells appears to elicit differentiation signals analogous to those delivered by the preB cell receptor in normal B cell development.
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Affiliation(s)
- K Nagata
- Department of Immunology, The Tokyo Metropolitan Institute of Medical Science, Japan
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43
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Lam KP, Kühn R, Rajewsky K. In vivo ablation of surface immunoglobulin on mature B cells by inducible gene targeting results in rapid cell death. Cell 1997; 90:1073-83. [PMID: 9323135 DOI: 10.1016/s0092-8674(00)80373-6] [Citation(s) in RCA: 862] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Gene targeting experiments have demonstrated that the expression of immunoglobulin heavy chain in the pre-B cell receptor (pBCR) and of heavy and light chains in the B cell antigen receptor (BCR) marks checkpoints in early B cell development that the cells have to pass to survive. To investigate whether the persistence of mature B cells in the peripheral immune system also depends on BCR expression, we have generated a transgenic mouse in which the BCR can be inducibly ablated through V region gene deletion. Ablation leads to rapid death of mature B lymphocytes, which is preceded by down-regulation of MHC antigens and up-regulation of CD95 (Fas) and can be delayed by constitutive bcl-2 expression.
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Affiliation(s)
- K P Lam
- Institute for Genetics, University of Cologne, Federal Republic of Germany
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44
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Akashi K, Kondo M, von Freeden-Jeffry U, Murray R, Weissman IL. Bcl-2 rescues T lymphopoiesis in interleukin-7 receptor-deficient mice. Cell 1997; 89:1033-41. [PMID: 9215626 DOI: 10.1016/s0092-8674(00)80291-3] [Citation(s) in RCA: 475] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mice lacking functional IL-7 or IL-7R alpha genes are severely deficient in developing thymocytes, T cells, and B cells. IL-7 and IL-7 receptor functions are believed to result in lymphoid cell proliferation and cell maturation, implying signal transduction pathways directly involved in mitogenesis and elaboration of developmentally specific new gene programs. Here, we show that enforced expression of the bcl-2 gene in T-lymphoid cells (by crossing in the Emu-bcl-2 transgene) in IL-7R alpha-deficient mice results in a significant restoration of thymic positive selection and T cell numbers and function. We propose cell survival signals to be the principal function of IL-7R engagement in thymic and T cell development.
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Affiliation(s)
- K Akashi
- Department of Pathology, Stanford University School of Medicine, California 94305, USA
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45
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Maraskovsky E, O'Reilly LA, Teepe M, Corcoran LM, Peschon JJ, Strasser A. Bcl-2 can rescue T lymphocyte development in interleukin-7 receptor-deficient mice but not in mutant rag-1-/- mice. Cell 1997; 89:1011-9. [PMID: 9215624 DOI: 10.1016/s0092-8674(00)80289-5] [Citation(s) in RCA: 402] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Signals from cytokine and antigen receptors play crucial roles during lymphocyte development. Mice lacking interleukin-7 receptor are lymphopenic, due to a defect in cell expansion at an early stage of differentiation, and the few mature T cells that develop in IL-7R-/- animals are functionally impaired. Both defects were rescued completely by overexpression of the anti-apoptosis protein Bcl-2. T cell progenitors lacking antigen receptor molecules are also blocked in differentiation and die, presumably because they fail to receive a positive signal via their pre-T cell receptor. Surprisingly, Bcl-2 did not promote survival or differentiation of T cells in rag-1-/- mice. These results provide evidence that blocking apoptosis is the essential function of IL-7R during differentiation and activation of T lymphocytes and that pre-TCR signaling blocks a pathway to apoptosis that is insensitive to Bcl-2.
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Affiliation(s)
- E Maraskovsky
- Department of Cellular Immunology, Immunex Research and Development Corporation, Seattle, Washington 98101, USA
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