Browsing by keyword "Antigens, CD80"
Now showing items 1-4 of 4
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Blockade of CD40-mediated signaling is sufficient for inducing islet but not skin transplantation toleranceTreatment of mice with a single donor-specific transfusion (DST) plus a brief course of anti-CD154 mAb to block CD40-mediated signaling uniformly induces donor-specific transplantation tolerance. Survival of islet allografts in treated mice is permanent, but skin grafts eventually fail unless recipients are thymectomized. The nature of the cellular mechanisms involved and the basis for the difference in survival of islet vs skin allografts are not known. In this study, we used CD40 knockout mice to investigate the role of CD40-mediated signaling in each component of the tolerance induction protocol: the DST, the graft, and the host. When CD40-mediated signaling was eliminated in only the DST or the graft, islet allografts were rapidly rejected. However, when CD40 signaling was eliminated in the host, approximately 40% of the islet allografts survived. When CD40 signaling was eliminated in the DST, the graft, and the host, islet grafts survived long term (>84 days), whereas skin allografts were rapidly rejected ( approximately 13 days). We conclude that transplantation tolerance induction in mice treated with DST and anti-CD154 mAb requires blockade of CD40-mediated signaling in the DST, the graft, and the host. Blockade of CD40-mediated signaling is necessary and sufficient for inducing islet allograft tolerance and is necessary but not sufficient for long-term skin allograft survival. We speculate that a requirement for regulatory CD4(+) T cells in skin allograft recipients could account for this differential response to tolerance induction.
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Phenotypic and functional heterogeneity of EBV epitope-specific CD8+ T cellsHigh frequencies of EBV-specific CD8(+) T cells have been detected during acute EBV infection, yet persistent infection inevitably results. To address this issue, we characterized the phenotype and function of epitope-specific CD8(+) T cell populations from presentation with acute through latent infection. Considerable phenotypic and functional heterogeneity within, as well as between, two different epitope-specific populations was observed over time following acute infection. B7 EBV-encoded nuclear Ag (EBNA)-3A-specific CD8(+) T cells expressed only CD45RO from acute through latent EBV infection. A2 BMLF-1-specific CD8(+) T cells expressed CD45RO during acute infection and either CD45RA or CD45RO during latent EBV infection. This difference in CD45 isoform expression between the two epitope-specific populations did not translate into differences in perforin content, the ability to produce IFN-gamma, or the ability to proliferate in response to Ag in vitro. In individuals with latent EBV infection, the frequencies of A2 BMLF-1- or B7 EBNA-3A-specific CD8(+) T cells that expressed CD45RA, CD45RO, CD62 ligand, CCR7, and perforin were stable over time. However, the expression of CD62 ligand and CCR7 was significantly higher among EBNA-3A-specific CD8(+) T cells than among BMLF-1-specific CD8(+) T cells. Further work is necessary to understand how phenotypic and functional differences between EBV epitope-specific CD8(+) T cells are related to the biology of the virus and to the equilibrium between the virus and the host during persistent infection.
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Reduced alloreactive T-cell activation after alcohol intake is due to impaired monocyte accessory cell function and correlates with elevated IL-10, IL-13, and decreased IFNgamma levelsBACKGROUND: Immunosuppression associated with chronic alcohol use is characterized by reduced antigen-specific T-cell response and impaired delayed type hypersensitivity. Increasing evidence suggests in chronic alcohol consumption models that reduced antigen-specific T-cell proliferation is due to insufficient accessory cell function. Accessory cell function, a critical step in recognition of viral antigens, is reduced in chronic hepatitis C. The severity of hepatitis C is increased by alcohol consumption. Thus, we investigated the effects of alcohol consumption on accessory cell activity of monocytes in supporting alloreactive T-cell proliferation. METHODS: Alloreactive T-cell proliferation was evaluated in a one-way mixed lymphocyte reaction (MLR). Mononuclear cells were isolated by Ficoll density gradient and monocytes by adherence. Alcohol (0.8 g/kg body weight, an equivalent of approximately three drinks) was given to nonalcohol-consuming individuals and blood samples were collected before, 4 hr, or 18 hr after alcohol consumption. Alcohol in vitro was administered at concentrations of 25-100 mM. RESULTS: T-cell proliferation in MLR was significantly reduced in the presence of physiologically relevant concentrations of alcohol in vitro (25-100 mM ethanol) (p < 0.05). In vivo alcohol consumption also depressed proliferation in the MLR when stimulator cells were obtained 4 hr after alcohol consumption. MLR was not decreased, however, in the presence of alcohol-exposed responder cells and normal stimulator cells, suggesting that the accessory cell population and not T cells are affected by alcohol. Decreased accessory cell function was further evidenced by reduced superantigen-induced (SEB) but not mitogen-induced (PHA) T-cell proliferation in samples obtained 18 hr after alcohol intake (35% reduction). Reduced accessory cell function was not due to changes in surface expression of monocyte costimulatory molecules (HLA class I, HLA-DR, CD80, CD86, CD40). We found reduced IFNgamma, elevated IL-10, and unchanged IL-4 levels during T-cell proliferation in samples obtained 18 hr after alcohol consumption. Acute alcohol treatment resulted in increased IL-13 in the MLR. CONCLUSION: These data suggest that even on one occasion moderate alcohol intake can reduce allostimulatory T-cell activation via decreasing accessory cell function. Increased IL-10 and IL-13 plus the reduced IFNgamma production after acute alcohol use are likely to contribute to both the reduced T-cell proliferation and monocyte accessory cell function. These accessory cell mediated defects in T-cell activation may result in impaired antiviral and antitumor immunity after moderate acute alcohol use.
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The role of B7-1 and B7-2 costimulation for the generation of CTL responses in vivoThe role of B7-1 and B7-2 costimulatory molecules in the generation of Ag-specific CD8+ CTLs is not well understood. In this paper, we analyze the role of both B7-1 and B7-2 in the generation of CTLs to nonliving, exogenous Ag and to live virus. To analyze the role of B7 costimulation in the induction of CTLs, we blocked B7-1 and/or B7-2 in vivo by injecting C57BL/6 mice with anti-B7-1 and/or anti-B7-2 mAbs; the mice were subsequently immunized with either chicken OVA that had been cross-linked to beads as a model of exogenous Ags or with wild-type and recombinant vaccinia virus expressing different forms of chicken OVA as models of viral Ags. Our results indicate that B7 costimulation is necessary in the generation of CTLs for all of these Ags. Since the B7 molecules could be costimulating CD8+ and/or CD4+ T cells in wild-type animals, we also examined the role of costimulation in the generation of CTLs to exogenous and viral Ag in MHC class II-deficient mice lacking most CD4+ T cells. In these animals, a combination of both mAbs also blocked all CTL responses, indicating that the Th cell-independent activation of CTLs is dependent upon the B7-costimulatory signals supplied to the CD8+ cell. These findings contribute to the understanding of the role of costimulation for the generation of CTLs. We also discuss the implications of these findings on the role of professional APCs in the initiation of CTL responses.