IMMUNOREGULATION OF MURINE CD8+ T CELLS

我们实验室最近的工作表明，Fas配体（FasL或CD 95 L），最有名的是通过与Fas相互作用传递死亡信号，也能够正向反向信号。因此，缺乏功能性FasL的CD 8 + T细胞相对于其FasL+对应物表现出抑制的抗原特异性增殖，并且FasIgG融合蛋白可以抑制野生型CD 8+细胞的应答。这些发现将FasL置于越来越多的能够进行双极信号传导的肿瘤坏死因子超家族成员之列-既可以通过其受体传递信号，也可以在配体结合后向内转导信号。拟议的实验的第一个目标是探索FasL介导的共刺激的性质，通过调查FasL分子的哪些区域是必需的，以及FasL与Fas以外的分子的结合是否可以启动反向信号传导。第二个总体目标是确定这种反向信号传导对成熟外周T细胞和发育中的胸腺细胞的体内相关性。具体目的如下：具体目的1：确定FasL的胞质尾区是否是反向信号传导所需的，以确定该结构域中的关键残基，并鉴定相关分子。目的二：探讨FasL信号在体内调节CD 8 + T细胞应答和胸腺内T细胞分化中的作用。具体目标3：继续研究Fas以外的分子诱导的FasL介导的共刺激，并通过表达克隆鉴定和表征该分子。

Recent work in our lab has demonstrated that Fas ligand (FasL or CD95L), best known for delivering a death signal through its interaction with Fas, is also capable of positive reverse signaling. Thus, CD8+ T cells lacking functional FasL exhibit depressed antigen-specific proliferation relative to their FasL+ counterparts, and FasIgG fusion proteins can inhibit the response of wildtype CD8+ cells. These findings place FasL among the growing number of tumor necrosis factor superfamily members capable of bipolar signaling -- both of delivering signals through their receptors and of transducing signals inward upon ligand binding. The first goal of the proposed experiments is to explore the nature of FasL-mediated costimulation by investigating what regions of the FasL molecule are required and whether binding of FasL to molecules other than Fas can initiate reverse signaling. The second overall goal is to determine the in vivo relevance of this reverse signaling, both for mature peripheral T cells and for developing thymocytes. The Specific Aims are as follows: Specific Aim 1: To determine whether the cytoplasmic tail of FasL is required for reverse signaling, to pinpoint critical residues in this domain, and to identify associated molecules. Specific Aim 2: To explore the in vivo role of FasL signaling in the regulation of CD8+ T cell responses and intrathymic T cell differentiation. Specific Aim 3: To continue to investigate FasL-mediated costimulation induced by a molecule other than Fas, and to identify and characterize this molecule by expression cloning.