IMMUNOREGULATION OF MURINE CD8+ T CELLS

我们实验室最近的工作表明，Fas配体(FasL或CD95L)，通过与Fas的相互作用传递死亡信号而闻名，也能够发出正向反向信号。因此，与FasL+T细胞相比，缺乏FasL功能的CD8+T细胞表现出抗原特异性的增殖抑制，而FasIgG融合蛋白可以抑制野生型CD8+细胞的反应。这些发现使FasL成为越来越多的能够传递双极信号的肿瘤坏死因子超家族成员之一--既可以通过它们的受体传递信号，也可以在配体结合时向内传递信号。实验的第一个目的是通过研究FasL分子的哪些区域是必需的，以及FasL与Fas以外的分子结合是否可以启动反向信号来探索FasL介导的共刺激的本质。第二个总体目标是确定这种反向信号在体内的相关性，无论是对成熟的外周T细胞还是对发育中的胸腺细胞。具体目标如下：特定目标1：确定FasL的细胞质尾部是否是反向信号所必需的，确定该结构域中的关键残基，并确定相关分子。特异性目的2：探讨FasL信号在体内调节CD8+T细胞应答和胸腺内T细胞分化中的作用。具体目的3：继续研究Fas以外的分子诱导的FasL介导的共刺激作用，并通过表达克隆鉴定和鉴定该分子。

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.