Cytotoxic Cells and Alloimmune Responses

描述（由申请方提供）：本项目的主要目的是阐明细胞毒性效应机制在同种免疫应答演变中的作用。拟议的研究将集中在颗粒巯基蛋白酶，二肽基肽酶I（DPPI），在细胞毒性T淋巴细胞（CTL）效应功能的产生和急性和慢性T细胞反应的调节中的作用。该项目支持的先前研究首次认识到DPPI在CTL、自然杀伤细胞、肥大细胞和嗜中性粒细胞的专门效应颗粒中高水平表达，其中该酶负责这些免疫效应细胞表达的颗粒丝氨酸蛋白酶的翻译后加工和活化。通过选择性蛋白酶抑制剂抑制DPPI功能或通过DPPI基因中的靶向突变缺失DPPI表达消除了颗粒酶A和颗粒酶B的加工和活化，并防止了穿孔素/颗粒酶依赖性机制诱导靶细胞凋亡。初步研究表明，DPPI缺陷型和穿孔素缺陷型CTL在诱导靶细胞凋亡方面表现出相似的缺陷，但DPPI和穿孔素缺陷型对免疫应答过程中CD 8 + T细胞增殖和扩增的影响明显不同。DPPI缺陷和/或抑制，但不是穿孔素缺陷与降低初始CD 8 + T细胞增殖反应次最大的刺激。此外，在将穿孔素缺陷型CD 8 + T细胞转移至MHC I类不同宿主后，观察到产生Tc 1细胞因子的CD 8 + T细胞的扩增显著增加，但在将DPPI缺陷型CD 8 + T细胞转移至MHC I类不同宿主后未观察到。未来的研究将探讨DPPI与穿孔素缺乏对T细胞功能影响差异的机制。我们还将讨论DPPI缺乏可能具有不同的影响，比穿孔素缺乏对移植物抗宿主病（GVHD）的演变的假设。这些后者的研究将检查穿孔素/颗粒酶细胞毒性效应机制在介导肝脏和肠道GVHD的作用，并应提供新的见解的作用，这种效应机制在骨髓和器官移植的并发症。

DESCRIPTION (provided by applicant): The broad objective of this project is to elucidate the role of cytotoxic effector mechanisms in the evolution of alloimmune responses. Proposed studies will focus on the role of the granule thiol protease, dipeptidyl peptidase I (DPPI), in both the generation of cytotoxic T lymphocyte (CTL) effector function and in the regulation of acute and chronic T cell responses. Prior studies supported by this project were the first to recognize that DPPI is expressed at high levels in the specialized effector granules of CTL, natural killer cells, mast cells and neutrophils where this enzyme is responsible for post-translational processing and activation of the granule serine proteases expressed by these immune effector cells. Inhibition of DPPI function by selective protease inhibitors or deletion of DPPI expression by targeted mutations in the DPPI gene abolishes processing and activation of Granzyme A and Granzyme B and prevents induction of target cell apoptosis by perforin/granzyme dependent mechanisms. Preliminary studies indicate that DPPI deficient and perforin deficient CTL exhibit similar defects in induction of target cell apoptosis, but DPPI and perforin deficiency have distinctly different effects on CD8+ T cell proliferation and expansion during immune responses. DPPI deficiency and/or inhibition but not perforin deficiency is associated with reduced initial CD8+ T proliferative responses to sub-maximal stimuli. In addition, dramatically increased expansion of Tc1 cytokine producing CD8+ T cells is observed after transfer of perforin deficient CD8+ T cells but not after transfer of DPPI deficient CD8+ T cells to MHC Class I disparate hosts. Proposed future studies will examine the mechanisms underlying these differences in effects of DPPI versus perforin deficiency on T cell function. We also will address the hypothesis that DPPI deficiency likely has different effects than perforin deficiency on the evolution of graft versus host disease (GVHD). These latter studies will examine the role of perforin/granzyme cytotoxic effector mechanisms in mediating liver and intestinal GVHD and should provide new insight into the role that such effector mechanisms play in the complications of bone marrow and organ transplantation.