51
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Qadri A, Radu CG, Thatte J, Cianga P, Ober BT, Ober RJ, Ward ES. A role for the region encompassing the c" strand of a TCR V alpha domain in T cell activation events. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:820-9. [PMID: 10878356 DOI: 10.4049/jimmunol.165.2.820] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The distinct strand topology of TCR V alpha domains results in a flatter surface in the region encompassing the c" strand than the corresponding region in Ig V domains. In the current study a possible role for this region in T cell activation has been investigated by inserting a potential glycosylation site at V alpha residue 82. This residue is in proximity to the c" strand and distal to the putative interaction site for cognate peptide:MHC ligand. An additional N-linked carbohydrate at this position would create a protrusion on the V alpha domain surface, and this may interfere with TCR aggregation and/or recruitment of signaling molecules. The modified TCR has been expressed in transfected T cells, and the phenotype following stimulation has been compared with that of cells expressing the wild-type TCR. The mutation has significant effects on activation-induced cell death and TCR internalization, but, unexpectedly, does not affect IL-2 secretion. Furthermore, analyses with tetrameric, peptide:MHC class II complexes suggest that the mutation decreases the ability of the TCR to aggregate into a configuration compatible with avid binding by these multivalent ligands.
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MESH Headings
- Animals
- Antibodies, Monoclonal/analysis
- Apoptosis/genetics
- Apoptosis/immunology
- Cell Line
- Down-Regulation/genetics
- Down-Regulation/immunology
- Immunoblotting
- Interleukin-2/metabolism
- Lymphocyte Activation/genetics
- Mice
- Myelin Basic Protein/genetics
- Myelin Basic Protein/immunology
- Myelin Basic Protein/pharmacology
- Peptide Fragments/genetics
- Peptide Fragments/immunology
- Peptide Fragments/pharmacology
- Phosphotyrosine/immunology
- Protein Structure, Tertiary
- Receptors, Antigen, T-Cell, alpha-beta/antagonists & inhibitors
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/physiology
- Recombinant Proteins/immunology
- Recombinant Proteins/pharmacology
- T-Lymphocytes/cytology
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
- Transfection/immunology
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Affiliation(s)
- A Qadri
- Center for Immunology and Cancer Immunobiology Center, University of Texas Southwestern Medical Center, Dallas, TX 75235, USA
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52
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CD4 T lymphocytes are primed to express Fas ligand by CD4 cross-linking and to contribute to CD8 T-cell apoptosis via Fas/FasL death signaling pathway. Blood 2000. [DOI: 10.1182/blood.v96.1.195.013k51_195_202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CD4 molecules serve as coreceptors for the T-cell receptor (TCR)/CD3 complex that are engaged coordinately with TCR and facilitate antigen-specific T-cell activation leading to interleukin 2 (IL-2) production and proliferation. However, cross-ligation of CD4 molecules prior to TCR stimulation has been shown to prime CD4 T cells to undergo apoptosis. Although in vivo and in vitro experiments have implicated the involvement of Fas/FasL interaction in this CD4 cross-linking (CD4XL)-induced apoptosis, detailed mechanisms to account for cell death induction have not been elucidated. In the present study, we demonstrate that CD4XL in purified T cells not only led to Fas up-regulation but also primed CD4 T cells to express FasL upon CD3 stimulation and rendered the T cells susceptible to Fas-mediated apoptosis. Notably, in addition to CD4+ T cells, CD4XL-induced sensitization for apoptosis was observed in CD8+ T cells as well and was associated with Bcl-x down-modulation. Both CD4 and CD8 T-cell subsets underwent apoptosis following cell–cell contact with FasL+ CD4 T cells. CD28 costimulation abrogated CD4XL/CD3-induced apoptosis with restoration of IL-2 production and prevented Bcl-x down-modulation. As CD4 molecules are the primary receptors for human immunodeficiency virus 1 (HIV-1), we conclude that HIV-1 envelope mediated CD4XL can lead to the generation of FasL-expressing CD4+ T cells that can lead to apoptosis of CD4 as well as CD8 T cells. These findings implicate a novel mechanism for CD8 T-cell depletion in HIV disease.
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53
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CD4 T lymphocytes are primed to express Fas ligand by CD4 cross-linking and to contribute to CD8 T-cell apoptosis via Fas/FasL death signaling pathway. Blood 2000. [DOI: 10.1182/blood.v96.1.195] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
CD4 molecules serve as coreceptors for the T-cell receptor (TCR)/CD3 complex that are engaged coordinately with TCR and facilitate antigen-specific T-cell activation leading to interleukin 2 (IL-2) production and proliferation. However, cross-ligation of CD4 molecules prior to TCR stimulation has been shown to prime CD4 T cells to undergo apoptosis. Although in vivo and in vitro experiments have implicated the involvement of Fas/FasL interaction in this CD4 cross-linking (CD4XL)-induced apoptosis, detailed mechanisms to account for cell death induction have not been elucidated. In the present study, we demonstrate that CD4XL in purified T cells not only led to Fas up-regulation but also primed CD4 T cells to express FasL upon CD3 stimulation and rendered the T cells susceptible to Fas-mediated apoptosis. Notably, in addition to CD4+ T cells, CD4XL-induced sensitization for apoptosis was observed in CD8+ T cells as well and was associated with Bcl-x down-modulation. Both CD4 and CD8 T-cell subsets underwent apoptosis following cell–cell contact with FasL+ CD4 T cells. CD28 costimulation abrogated CD4XL/CD3-induced apoptosis with restoration of IL-2 production and prevented Bcl-x down-modulation. As CD4 molecules are the primary receptors for human immunodeficiency virus 1 (HIV-1), we conclude that HIV-1 envelope mediated CD4XL can lead to the generation of FasL-expressing CD4+ T cells that can lead to apoptosis of CD4 as well as CD8 T cells. These findings implicate a novel mechanism for CD8 T-cell depletion in HIV disease.
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54
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Wiegers GJ, Stec IE, Klinkert WE, Reul JM. Glucocorticoids regulate TCR-induced elevation of CD4: functional implications. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 164:6213-20. [PMID: 10843673 DOI: 10.4049/jimmunol.164.12.6213] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CD4 serves as a coreceptor during Ag recognition by the TCR. This interaction results in a marked increase in the sensitivity of a T cell to Ag presented by MHC class II molecules. Here we report that activation of T cells either by plate-bound mAb (anti-TCR, anti-CD3) or soluble activators (staphylococcal enterotoxin A, Con A) is associated with an (up to 3-fold) increase in CD4 cell surface expression on CD25+ cells, which was maximal after 72-96 h. Incubation with the glucocorticoid hormone corticosterone (CORT) shifted the enhancement of CD4 expression to a point about 24 h earlier than that observed in control cultures. In parallel, the proliferative response of these CORT-treated cells was profoundly enhanced. An involvement of increased CD4 expression in this enhanced proliferative response was evidenced by the observation that T cell proliferation in CORT-treated cultures was much less sensitive to inhibition by an inhibitory, nondepleting anti-CD4 mAb than that in control cultures. TCR down-regulation was, however, not affected by CORT. Thus, based on this study and previous reports we propose that both TCR-mediated signals and glucocorticoids are important physiological regulators of CD4 expression. In addition, these findings may be of significance for the sensitivity of CD4+ cells to HIV infection upon T cell activation, as the efficacy of primary patient HIV entry depends on the level of surface CD4.
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MESH Headings
- Adjuvants, Immunologic/antagonists & inhibitors
- Adjuvants, Immunologic/pharmacology
- Animals
- Antibodies, Monoclonal/pharmacology
- CD4 Antigens/biosynthesis
- CD4 Antigens/immunology
- CD4 Antigens/physiology
- CD4-Positive T-Lymphocytes/immunology
- Cells, Cultured
- Corticosterone/antagonists & inhibitors
- Corticosterone/pharmacology
- Corticosterone/physiology
- Down-Regulation/drug effects
- Down-Regulation/immunology
- Lymphocyte Activation/drug effects
- Lymphocyte Activation/immunology
- Male
- Mifepristone/pharmacology
- Rats
- Rats, Wistar
- Receptors, Antigen, T-Cell/antagonists & inhibitors
- Receptors, Antigen, T-Cell/biosynthesis
- Receptors, Antigen, T-Cell/physiology
- Receptors, Glucocorticoid/antagonists & inhibitors
- T-Lymphocytes/drug effects
- T-Lymphocytes/immunology
- T-Lymphocytes/metabolism
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Affiliation(s)
- G J Wiegers
- Section of Neuroimmunoendocrinology, Max Planck Institute of Psychiatry, Munich, Germany
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55
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Fujii S. Role of interferon-alpha and clonally expanded T cells in the immunotherapy of chronic myelogenous leukemia. Leuk Lymphoma 2000; 38:21-38. [PMID: 10811445 DOI: 10.3109/10428190009060316] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Twenty five percent of patients in the chronic phase of chronic myelogenous leukemia (CML) are treated with interferon-alpha (IFN-alpha) to induce a cytogenic remission. In addition to its direct effects on leukemic cells, IFN-alpha has been shown to induce immunologic alterations, including upregulation of the expression of major histocompatibility (MHC) antigens in antigen-presenting cells (APCs), as well as augmentation of the activity of the lymphocytes against tumor cells. However, there has been little direct evidence supporting a causal interaction between cellular immunoreactivity and clinical responsiveness to IFN-alpha. We have shown that one approach to elucidate the immunological mechanisms by which IFN-alpha exerts its anti-CML activity is by analyzing therapy-induced modulation in T-cell receptor (TCR) Vbeta chain usage, using the reverse transcription-polymerase chain reaction (RT-PCR) followed by single-strand conformation (SSCP) analysis. This method is particularly attractive, since it provides an index of antigen-specific T cell expansion, but does not require the extraction and purification of the antigens involved in the T-cell response. T cell clones that express the Vbeta 10, 12, and 14 families predominate in the peripheral blood (PB) of CML patients. The enhanced expression of the Vbeta 9 and 20 families has been detected in IFN-alpha responsive patients but not patients who are poorly responsive to this agent. This suggests that expansion of T cells expressing these TCR Vbeta gene families may serve as a prognostic factors of the clinical responsiveness of CML patients to IFN-alpha. In addition, since T cell clones that express certain Vbeta families may react with a discrete set of antigenic peptides presented on the surface of malignant cells, a better understanding of the immunobiology of T cells in CML may allow for the design of increasing efficacious immune therapy for this disease.
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Affiliation(s)
- S Fujii
- The Center for Bone Marrow Transplantation and Immunotherapy, Institute for Clinical Research, Kumamoto National Hospital, Japan.
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56
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Somma F, Tuosto L, Gilardini Montani MS, Di Somma MM, Cundari E, Piccolella E. Engagement of CD4 before TCR triggering regulates both Bax- and Fas (CD95)-mediated apoptosis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 164:5078-87. [PMID: 10799864 DOI: 10.4049/jimmunol.164.10.5078] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In the present study, we have aimed at clarifying the CD4-dependent molecular mechanisms that regulate human memory T cell susceptibility to both Fas (CD95)-dependent and Bcl-2-dependent apoptotic pathways following antigenic challenge. To address this issue, we used an experimental system of viral and alloantigen-specific T cell lines and clones and two ligands of CD4 molecules, Leu-3a mAb and HIV gp120. We demonstrate that CD4 engagement before TCR triggering suppresses the TCR-mediated neosynthesis of the Flice-like inhibitory protein and transforms memory T cells from a CD95-resistant to a CD95-susceptible phenotype. Moreover, evidence that the apoptotic programs were executed while Fas ligand mRNA expression was inhibited led us to analyze Bcl-2-dependent pathways. The data show that the engagement of CD4 separately from TCR influences the expression of the proapoptotic protein Bax independently of the anti-apoptotic protein Bcl-2, whereas Ag activation coordinately modulates both Bax and Bcl-2. The increased expression of Bax and the consequent dissipation of the mitochondrial transmembrane potential (DeltaPsim) suggest a novel immunoregulatory function of CD4 and demonstrate that both passive cell death and activation-induced cell death are operative in CD4+ memory T cells. Furthermore, analysis of the mechanisms by which IL-2 and IL-4 cytokines exert their protective function on CD4+ T cells in the presence of soluble CD4 ligands shows that they were able to revert susceptibility to Bax-mediated but not to CD95-dependent apoptotic pathways.
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Affiliation(s)
- F Somma
- Department of Cellular and Developmental Biology, "La Sapienza" University, Rome, Italy
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57
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Dockrell DH, Badley AD, Algeciras-Schimnich A, Simpson M, Schut R, Lynch DH, Paya CV. Activation-induced CD4+ T cell death in HIV-positive individuals correlates with Fas susceptibility, CD4+ T cell count, and HIV plasma viral copy number. AIDS Res Hum Retroviruses 1999; 15:1509-18. [PMID: 10580401 DOI: 10.1089/088922299309793] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The relevance of activation-induced cell death (AICD) of CD4+ T cells to AIDS pathogenesis is unknown. The present study investigates the relationship of AICD to a defined molecular mechanism regulating peripheral T cell homeostasis, Fas-mediated apoptosis, and clinical correlates of the pathogenesis of AIDS. Increased pokeweed mitogen (PWM)-induced AICD (22.8 versus 4.4%, p = 0.006) and Fas-mediated apoptosis (27.7 versus 12.0%, p = 0.002) of CD4+ T cells were observed in HIV+ versus HIV- individuals. Similarly, increased PWM-mediated AICD (16.2 versus 2.2%, p < 0.001) and Fas-mediated apoptosis (25.8 versus 7.6%, p = 0.005) were noted in CD8+ T cells from HIV+ versus HIV- individuals. PWM-induced AICD of CD4+ T cells was blocked (83% median specific inhibition) by Fas-blocking antibodies, whereas PWM-induced AICD of CD8+ T cells was Fas independent. Comparison between PWM- and anti-CD3-mediated AICD of CD4+ T cells indicated that PWM- and not CD3-induced AICD is Fas dependent. HIV+ individuals with an HIV RNA copy number of <30,000 copies/ml had lower PWM-induced AICD of CD4+ T cells than did those with an HIV RNA copy number of >30,000 copies/ml (5.7 versus 22.1%, p = 0.034), and PWM-induced AICD inversely correlated with CD4+ T cell count (R = -0.567, p = 0.043). Initiation of HAART decreased PWM-induced CD4+ T cell AICD from 24.4 to 9.4% posttreatment (p = 0.035). These results demonstrate that PWM-induced AICD of CD4+ T cells from HIV+ individuals is mediated by Fas/FasL, parallels the in vivo susceptibility of the CD4+ T cell to Fas-mediated apoptosis, and correlates with clinical markers of AIDS pathogenesis and response to HAART.
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Affiliation(s)
- D H Dockrell
- Division of Infectious Diseases, Mayo Clinic, Rochester, Minnesota 55905, USA
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58
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Bottarel F, Feito MJ, Bragardo M, Bonissoni S, Buonfiglio D, DeFranco S, Malavasi F, Bensi T, Ramenghi U, Dianzani U. The cell death-inducing ability of glycoprotein 120 from different HIV strains correlates with their ability to induce CD4 lateral association with CD95 on CD4+ T cells. AIDS Res Hum Retroviruses 1999; 15:1255-63. [PMID: 10505674 DOI: 10.1089/088922299310151] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CD4 cross-linking by HIV gp120 triggers CD4+ T cell death. Several authors have suggested that this effect is mediated by CD95, but this possibility is debated by other authors. In a previous work, we found by co-capping that gp120(451) and gp120MN, but not gp120(IIIB), induce lateral association of CD4 with CD95 on the T cell surface. In this work, we used fluorescence resonance energy transfer to confirm that CD4/CD95 lateral association is induced by gp120(451), but not gp120(IIIB). Moreover, we found that gp120 ability to induce the CD4/CD95 association correlates with ability to induce cell death, since gp120(451) and gp120MN induced higher levels of cell death than did gp120(IIIB) in PHA-derived CD4+ T cell lines. CD95 involvement in gp120-induced cell death was confirmed by showing that gp120(451) and gp120MN did not induce death in CD4+ T cells derived from patients with autoimmune/lymphoproliferative disease (ALD) and decreased CD95 function. Cell death induced by gp120MN was inhibited by a recombinant CD95/IgG.Fc molecule blocking the CD95/CD95L interaction. However, inhibition was late and only partial. These data suggest that the gp120-induced CD4/CD95 association exerts a dual effect: an early effect that is independent of CD95L and may be due to direct triggering of CD95 by gp120, and a late effect that may be due to sensitization of CD95 to triggering by CD95L. In line with the former effect, cell treatment with gp120MN activated caspase 3 in the presence of Fas/IgG.Fc, which shows that cell death induced by gp120MN independently of CD95L uses the same pathway as CD95.
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Affiliation(s)
- F Bottarel
- Department of Medical Sciences, A. Avogadro University of Eastern Piedmont at Novara, Italy
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59
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Sanzenbacher R, Kabelitz D, Janssen O. SLP-76 Binding to p56 lck: A Role for SLP-76 in CD4-Induced Desensitization of the TCR/CD3 Signaling Complex. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.163.6.3143] [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
Nonreceptor protein tyrosine kinases and associated substrates play a pivotal role in Ag receptor stimulation of resting cells and in the initiation of activation-induced cell death (AICD) of preactivated T cells. CD4-associated p56lck has been implicated not only in the activation of primary T cells, but also in the inhibition of T cell responses. We have previously shown that CD4+ T cell clones can be rescued from AICD when surface CD4 is engaged before the TCR stimulus. In this study, we show that prevention of AICD is associated with a CD4-dependent inhibition of TCR-triggered tyrosine phosphorylation of the Src homology 2 domain-containing leukocyte protein of 76 kDa (SLP-76) and Vav. We provide evidence for a SLP-76 interaction with Src homology 3 domains of p56lck and identify amino acids 185–194 of SLP-76 as relevant docking site. In view of the multiple functions of p56lck and SLP-76/Vav in the initiation of TCR/CD3/CD4 signaling, we propose a model for the CD4-dependent inhibition of TCR signaling and AICD of preactivated T cells. Our data suggest that preformed activation complexes of adapter proteins and enzymes in the vicinity of the CD4/p56lck complex are no longer available for the TCR signal when CD4 receptors are engaged before TCR stimulation.
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Affiliation(s)
| | - Dieter Kabelitz
- Department of Immunology, Paul-Ehrlich-Institute, Langen, Germany
| | - Ottmar Janssen
- Department of Immunology, Paul-Ehrlich-Institute, Langen, Germany
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60
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Pettersen RD, Hestdal K, Olafsen MK, Lie SO, Lindberg FP. CD47 Signals T Cell Death. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.12.7031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
Activation-induced death of T cells regulates immune responses and is considered to involve apoptosis induced by ligation of Fas and TNF receptors. The role of other receptors in signaling T cell death is less clear. In this study we demonstrate that activation of specific epitopes on the Ig variable domain of CD47 rapidly induces apoptosis of T cells. A new mAb, Ad22, to this site induces apoptosis of Jurkat cells and CD3ε-stimulated PBMC, as determined by morphological changes, phosphatidylserine exposure on the cell surface, uptake of propidium iodide, and true counts by flow cytometry. In contrast, apoptosis was not observed following culture with anti-CD47 mAbs 2D3 or B6H12 directed to a distant or closely adjacent region, respectively. CD47-mediated cell death was independent of CD3, CD4, CD45, or p56lck involvement as demonstrated by studies with variant Jurkat cell lines deficient in these signaling pathways. However, coligation of CD3ε and CD47 enhanced phosphatidylserine externalization on Jurkat cells with functional CD3. Furthermore, normal T cells required preactivation to respond with CD47-induced apoptosis. CD47-mediated cell death appeared to proceed independent of Fas or TNF receptor signaling and did not involve characteristic DNA fragmentation or requirement for IL-1β-converting enzyme-like proteases or CPP32. Taken together, our data demonstrate that under appropriate conditions, CD47 activation results in very rapid T cell death, apparently mediated by a novel apoptotic pathway. Thus, CD47 may be critically involved in controlling the fate of activated T cells.
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Affiliation(s)
| | | | | | - Sverre O. Lie
- †Pediatrics, The National Hospital, Oslo, Norway; and
| | - Frederik P. Lindberg
- ‡Department of Infectious Diseases, Washington University School of Medicine, St. Louis, MO 63110
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61
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Maini MK, Casorati G, Dellabona P, Wack A, Beverley PC. T-cell clonality in immune responses. IMMUNOLOGY TODAY 1999; 20:262-6. [PMID: 10354551 DOI: 10.1016/s0167-5699(99)01472-3] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recent methodological advances allow the analysis of clonal composition within T-cell subsets. Here, Mala Maini and colleagues review the available data on clonality in acute immune responses and steady-state situations. They highlight and explore reasons for the striking differences in clonality between the CD4+ and CD8+ T-cell subsets.
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Affiliation(s)
- M K Maini
- Dept of Sexually Transmitted Diseases, Royal Free and University College Medical School, Mortimer Market off Capper St, London, UK WC1E 6AU.
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62
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Maroto R, Shen X, König R. Requirement for Efficient Interactions Between CD4 and MHC Class II Molecules for Survival of Resting CD4+ T Lymphocytes In Vivo and for Activation-Induced Cell Death. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.10.5973] [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
Regulation of homeostasis in the immune system includes mechanisms that promote survival of resting T lymphocytes, and others that control activation-induced cell death (AICD). In this study, we report on the use of a transgenic mouse model to test the role of CD4-MHC class II interactions for the susceptibility of CD4+ T lymphocytes to AICD, and for the survival of resting CD4+ T cells in peripheral lymphoid organs. The only I-Aβ gene expressed in these mice is an Aβk transgene with a mutation that prevents MHC class II molecules from interacting with CD4. We show increased apoptosis in CD4+ T lymphocytes derived from wild-type, but not from mutant Aβk transgenic mice following stimulation with staphylococcal enterotoxin A. Therefore, AICD may be impaired in CD4+ T cells derived from mutant Aβk transgenic mice. Importantly, we observed much higher apoptosis in resting CD4+ T cells from mutant Aβk transgenic mice than from wild-type mice. Furthermore, resting CD4+ T cells from mutant Aβk transgenic mice expressed higher levels of cell surface CD95 (Fas, APO-1). Ab-mediated cross-linking of CD95 further increased apoptosis in CD4+ T cells from mutant Aβk transgenic mice, but not from wild-type mice, suggesting apoptosis involved CD95 signaling. When cocultured with APC-expressing wild-type MHC class II molecules, apoptosis in resting CD4+ T lymphocytes from mutant Aβk transgenic mice was reduced. Our results show for the first time that interactions between CD4 and MHC class II molecules are required for the survival of resting CD4+ T cells in peripheral lymphoid organs.
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Affiliation(s)
- Rosario Maroto
- Department of Microbiology and Immunology and Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, TX 77555
| | - Xiaoli Shen
- Department of Microbiology and Immunology and Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, TX 77555
| | - Rolf König
- Department of Microbiology and Immunology and Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, TX 77555
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63
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Yin C, Wu MS, Pauza CD, Salvato MS. High major histocompatibility complex-unrestricted lysis of simian immunodeficiency virus envelope-expressing cells predisposes macaques to rapid AIDS progression. J Virol 1999; 73:3692-701. [PMID: 10196261 PMCID: PMC104144 DOI: 10.1128/jvi.73.5.3692-3701.1999] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/1998] [Accepted: 01/13/1999] [Indexed: 11/20/2022] Open
Abstract
Before the development of virus-specific immune responses, peripheral blood mononuclear cells (PBMC) from uninfected rhesus monkeys and human beings have the capacity to lyse target cells expressing simian immunodeficiency virus (SIV) or human immunodeficiency virus-1 (HIV) envelope (gp130 and gp120) antigens. Lysis by naive effector cells does not require major histocompatibility complex (MHC)-restricted antigen presentation, is equally effective for allogeneic and xenogeneic targets, and is designated MHC-unrestricted (UR) lysis. UR lysis is not sensitive to EGTA and does not require de novo RNA or protein synthesis. Several kinds of envelope-expressing targets, including cells that poorly express MHC class I antigens, can be lysed. CD4(+) effectors are responsible for most of the lytic activity. High lysis is correlated with high expression of HIV or SIV envelope, specifically, the central one-third of the gp130 molecule, and lysis is completely inhibited by a monoclonal antibody against envelope. Our work extends observations of human lymphocytes expressing HIV gp120 to the SIV/rhesus monkey model for AIDS. Additionally, we address the relevance of UR lysis in vivo. A survey of PBMC from 56 uninfected rhesus monkeys indicates that 59% of the individuals had peak UR lytic activity above 15% specific lysis. Eleven of these monkeys were subsequently infected with SIV. Animals with UR lytic activity above 15% specific lysis were predisposed to more rapid disease progression than animals with low UR lytic activity, suggesting a strong correlation between this form of innate immunity and disease progression to AIDS.
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Affiliation(s)
- C Yin
- Department of Pathology and Laboratory Medicine, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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64
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Potter A, Kim C, Gollahon KA, Rabinovitch PS. Apoptotic human lymphocytes have diminished CD4 and CD8 receptor expression. Cell Immunol 1999; 193:36-47. [PMID: 10202111 DOI: 10.1006/cimm.1998.1443] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We used quantitative multiparameter flow cytometric assays to simultaneously detect viable, apoptotic, and necrotic human peripheral blood mononuclear cells (PBMC) and immunophenotyped lymphocyte subsets within the PBMC. Apoptosis was induced by a spectrum of treatments, including camptothecin, cisplatin, dexamethasone, hyperthermia, staurosporine, and etoposide in anti-CD3 mAb-stimulated cells and by cyclohexamide in both quiescent and stimulated cells; apoptosis in the latter was augmented by anti-fas mAb. We found that CD4(+) and CD8(+) cells were significantly underrepresented in the apoptotic PBMC and that the percentage of CD4(+) and CD8(+) PBMC each markedly decreased as apoptosis increased. This suggested that surface expression of these receptors was lessened on apoptotic CD4(+) and CD8(+) cells. This was directly confirmed by observation of sorted CD4(+) PBMC. This analysis of a wide variety of apoptotic stimuli demonstrates that diminished CD4 and CD8 surface receptor expression is a common feature of human T lymphocyte apoptosis.
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Affiliation(s)
- A Potter
- Department of Pathology, University of Washington, Seattle, Washington, 98195, USA
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65
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Mocchegiani E, Muzzioli M, Gaetti R, Veccia S, Viticchi C, Scalise G. Contribution of zinc to reduce CD4+ risk factor for 'severe' infection relapse in aging: parallelism with HIV. INTERNATIONAL JOURNAL OF IMMUNOPHARMACOLOGY 1999; 21:271-81. [PMID: 10408635 DOI: 10.1016/s0192-0561(99)00009-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Aging and HIV have parallelism in immunodeficiency status because of the appearance of infections or relapse leading to death in both conditions. HIV-RNA is predictor for HIV progression correlated with CD4+ depletion. CD4+ and plasma zinc levels (zincaemia) may be predictors for infections relapse in aging because of zinc relevance for normal immune efficiency against infections and for CD4+ growth. Moreover, zincaemia decreases in aging and infection. A total of 67 elderly subjects affected by infections resistant to antibiotic therapy were recruited. A total of 28 HIV+ subjects with HAART therapy were also used. CD4+ depletion (507 mm3) and zincaemia deficiency (76 microg/dl), as compared to CD4+ (700-1100 mm3) and zincaemia (85-100 microg/dl; age 40-75 years) normal ranges, are possible limits (Cox hazard regression) for severe infections relapse, such as chronic obstructive bronchitis and bronchopneumonia by bacteria or Candida complication, in aging. CD4+ and zincaemia values are within the lower limits of normal range in urinary tract infections. Zincaemia and HIV-RNA or CD4+ are inversely correlated (r = 0.57 and r = 0.72, respectively) in HIV+ HAART treated subjects. Consequently there is no appearance of opportunistic infections. Parallelism between aging and HIV may exist because of the resemblance in marked zinc deficiency and CD4+ depletion with high scores in relative risks for severe infections relapse. Supplementing zinc (12 mg Zn++/day) for one month in infected elderly subjects and HAART therapy in HIV+ subjects reduces risk scores in CD4+ and zincaemia deficiencies for infections relapse, suggesting that the zinc beneficial effect may be independent either by HIV-virus or pathogen agents involved. While HAART may reduce the occurrence of opportunistic infections in HIV by means of also major zinc bioavailability, supplementing zinc can be recommended in elderly people as resistance to infections. Since zinc deficiency is correlated with CD4+ depletion, this latter may also be good diagnostic marker to detect 'clear immunodeficiency' in aging, as in HIV condition.
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Affiliation(s)
- E Mocchegiani
- Immunology Centre, Gerontol, Res. Dept., N. Masera, Italian National Research Centres on Aging, Ancona.
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66
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Abstract
Viruses can induce apoptosis of infected cells either directly, to assist virus dissemination, or by inadvertently triggering cellular sensors that initiate cell death. Cellular checkpoints that can function as 'alarm bells' to transmit pro-apoptotic signals in response to virus infections include death receptors, protein kinase R, mitochondrial membrane potential, p53 and the endoplasmic reticulum.
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Affiliation(s)
- H Everett
- Dept of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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67
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Casella CR, Rapaport EL, Finkel TH. Vpu increases susceptibility of human immunodeficiency virus type 1-infected cells to fas killing. J Virol 1999; 73:92-100. [PMID: 9847311 PMCID: PMC103812 DOI: 10.1128/jvi.73.1.92-100.1999] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/1998] [Accepted: 09/25/1998] [Indexed: 01/07/2023] Open
Abstract
The importance of the Fas death pathway in human immunodeficiency virus (HIV) infection has been the subject of many studies. Missing from these studies is direct measurement of infected cell susceptibility to Fas-induced death. To address this question, we investigated whether T cells infected with HIV are more susceptible to Fas-induced death. We found that Fas cross-linking caused a decrease in the number of HIV-infected Jurkat T cells and CD4(+) peripheral blood leukocytes (PBLs). We confirmed this finding by demonstrating that there were more apoptotic infected than uninfected cells after Fas ligation. The increase in sensitivity of HIV-infected cells to Fas killing mapped to vpu, while nef, vif, vpr, and second exon of tat did not appear to contribute. Furthermore, expression of Vpu in Jurkat T cells rendered them more susceptible to Fas-induced death. These results show that HIV-infected cells are more sensitive to Fas-induced death and that the Vpu protein of HIV contributes to this sensitivity. The increased sensitivity of HIV-infected cells to Fas-induced death might help explain why these cells have such a short in vivo half-life.
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Affiliation(s)
- C R Casella
- Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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68
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Williams MS, Noguchi S, Henkart PA, Osawa Y. Nitric Oxide Synthase Plays a Signaling Role in TCR-Triggered Apoptotic Death. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.12.6526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Abstract
A functional role for stimulated nitric oxide (NO) production was tested in the TCR-triggered death of mature T lymphocytes. In purified peripheral human T cell blasts or the 2B4 murine T cell hybridoma, apoptotic cell death induced by immobilized anti-CD3 was blocked by inhibitors of NO synthase (NOS) in a stereospecific and concentration-dependent manner. This effect appeared to be selective since apoptotic death induced by anti-Fas Ab or the steroid dexamethasone was not affected by NOS inhibitors. TCR-stimulated expression of functional Fas ligand was attenuated in a stereospecific manner by NOS inhibitors, but these compounds did not inhibit TCR-stimulated IL-2 secretion or CD69 surface expression. Nitrosylated tyrosines, a stable marker for NO generation, were immunochemically detected in T cells using flow cytometry. TCR signals induced NO production, as measured by an increase in nitrotyrosine-specific staining. NOS enzymatic activity was detected in lysates of 2B4 cells, and Western blot analysis suggests that the activity is due to expression of the neuronal isoform of NOS. Thus, T cells have the capacity to generate NO upon Ag signaling, which may affect signal transduction, Fas ligand surface expression, and apoptotic cell death of mature T lymphocytes.
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Affiliation(s)
- Mark S. Williams
- *Department of Immunology, Holland Lab, American Red Cross, Rockville, MD 20855
| | - Soichi Noguchi
- ‡Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
| | - Pierre A. Henkart
- †Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; and
| | - Yoichi Osawa
- ‡Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109
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69
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Popik W, Pitha PM. Early activation of mitogen-activated protein kinase kinase, extracellular signal-regulated kinase, p38 mitogen-activated protein kinase, and c-Jun N-terminal kinase in response to binding of simian immunodeficiency virus to Jurkat T cells expressing CCR5 receptor. Virology 1998; 252:210-7. [PMID: 9875330 DOI: 10.1006/viro.1998.9466] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We have shown that the binding of simian immunodeficiency virus (SIV) to Jurkat T cells expressing CD4 receptor strongly induces mitogen-activated protein (MAP) kinase kinase (MEK) and extracellular signal-regulated kinases 1 and 2 (ERK1/2) and only weakly induces p38 MAP kinase and c-Jun N-terminal kinase (JNK). Similarly, T-tropic NL4-3 virus, which uses both CD4 and CXCR4 receptors for entry, stimulated in these cells the MEK/ERK MAP kinase (MAPK) pathway in a CD4 receptor-dependent manner (Popik and Pitha, 1998). In contrast, both macrophage-tropic SIVmac316 and T cell-tropic SIVmac239, which in addition to CD4 require CCR5 coreceptor for entry, significantly enhanced early MEK/ERK, p38 MAPK, and JNK signaling in Jurkat cells expressing constitutively or transiently the CCR5 receptor. Together, this study provides the evidence that viruses using CXCR4 or CCR5 receptors for entry may differentially use signaling properties of their specific coreceptors to stimulate MAP kinase cascades. In addition, although SIVmac239 and SIVmac316 use different structural domains of the CCR5 receptor for entry, both viruses stimulate early phosphorylation of MEK, ERK, p38, and JNK independently of their tropism and replication.
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Affiliation(s)
- W Popik
- Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231, USA.
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70
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Chin BY, Choi ME, Burdick MD, Strieter RM, Risby TH, Choi AM. Induction of apoptosis by particulate matter: role of TNF-alpha and MAPK. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L942-9. [PMID: 9815112 DOI: 10.1152/ajplung.1998.275.5.l942] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Particulate matter (PM) is a major by-product from the combustion of fossil fuels. The biological target of inhaled PM is the pulmonary epithelium and resident macrophages. In this study, we demonstrate that cultured macrophages (RAW 264.7 cells) exposed continously to a well-defined model of PM [benzo[a]pyrene adsorbed on carbon black (CB+BaP)] exhibit a time-dependent expression and release of the cytokine tumor necrosis factor-alpha (TNF-alpha). CB+BaP also evoked programmed cell death or apoptosis in cultured macrophages as assessed by genomic DNA-laddering assays. The CB+BaP-induced apoptosis was inhibited when macrophages were treated with CB+BaP in the presence of a neutralizing antibody to TNF-alpha, suggesting that TNF-alpha plays an important role in mediating CB+BaP-induced apoptosis in macrophages. Interestingly, neither untreated carbon black nor benzo[a]pyrene alone induced apoptosis or caused the release of TNF-alpha in RAW 264.7 cells. Moreover, we observed that TNF-alpha activates mitogen-activated protein kinase (MAPK) activity, the extracellular signal-regulated kinases p42/p44, in a time-dependent manner. RAW 264.7 cells treated with PD-098059, a selective inhibitor of MAPK kinase activity, did not exhibit CB+BaP-induced apoptosis and TNF-alpha secretion. Furthermore, cells treated with the MAPK kinase inhibitor did not undergo TNF-alpha-induced apoptosis. Taken together, our data suggest that TNF-alpha mediates PM-induced apoptosis and that the MAPK pathway may play an important role in regulating this pathway.
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Affiliation(s)
- B Y Chin
- Division of Pulmonary and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21205, USA
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71
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Abstract
Tumors of diverse origin have recently been shown to express CD95 ligand and to induce apoptosis in CD95-expressing targets in vitro; however, in vivo, enhanced tumor growth and rejection have both been observed as a consequence of either immunosuppressive or proinflammatory functions of CD95 ligand. The final in vivo outcome of CD95 ligand expression will depend upon a complex balance of interactions relevant for each tumor in its particular microenvironment.
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Affiliation(s)
- P R Walker
- Laboratory of Tumour Immunology, Division of Oncology, University Hospital Geneva, 24 rue Micheli-du-Crest, CH-1211, Geneva 14, Switzerland.
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