Costimulatory regulation of CD8 T cell tolerance

描述(申请人提供)：控制自身组织免疫耐受的分子机制仍不清楚；这些机制的崩溃可能导致包括胰岛素依赖型糖尿病在内的自身免疫性疾病。CD8+细胞毒性T(TC)细胞在自身免疫性糖尿病的发病机制中起关键作用。为什么TC细胞通常对胰腺抗原具有耐受性，以及自身反应性TC细胞在自身免疫性糖尿病中如何被激活，目前尚不清楚。交叉启动已被认为是MHC I类递呈细胞相关抗原的一种常见机制。RIP-OVA小鼠的研究表明，在胰岛表达的鸡卵清蛋白可由引流淋巴结的树突状细胞递送给T细胞，从而导致自身反应性CD8细胞的交叉耐受。T细胞激活与耐受的决定最重要的是由抗原提呈细胞(APC)上的共刺激信号调节的。在目前的研究中，我们建议使用RIP-OVA小鼠来验证我们的假设，即TC细胞的激活和耐受受到正负共刺激分子的严格调控。首先，我们将分析CD28和ICOS在调节TC细胞激活中的作用。我们将ICOS+/+和ICOS-/-OT-I细胞转移到B7.1和B7.2基因充足或缺陷的RIP-Mova转基因小鼠中，并检测它们的激活和耐受性。其次，我们将研究PDL2、B7-H3和B7S1在调节TC细胞耐受中的作用。我们将OT-T细胞转移到RIP-Mova小鼠体内，无论是否用抗PDL2、BT-H3或B7S1封闭抗体处理，并检测转移细胞的活化或耐受性。这项研究将促进我们对TC激活和耐受性的共刺激调节的理解，并可能提出调节对组织抗原的免疫耐受性的方法。

DESCRIPTION (provided by applicant): The molecular mechanisms which govern immune tolerance to self tissues are still not understood; the breakdown of these mechanisms can lead to autoimmune diseases including insulin-dependent diabetes. CD8+ cytotoxic T (Tc) cells play a key role in pathogenesis of autoimmune diabetes in mouse and human. Why Tc cells are normally tolerant to pancreatic antigens and how autoreactive Tc cells become activated in autoimmune diabetes is unclear. Cross-priming has been indicated as a common mechanism for MHC class I presentation of cell-associated antigen. It has been shown by use of RIP-Ova mice that chicken ovalbumin protein expressed in the pancreatic islets can be presented by dendritic cells in draining lymph nodes to Tc cells, which results in cross-tolerance of self-reactive CD8 cells. The decision of T cell activation vs. tolerance is most importantly regulated by costimulatory signals on antigen-presenting cells (APC). In the current study, we propose to test our hypothesis that Tc cell activation and tolerance are tightly regulated by the positive and negative costimulatory molecules by use of the RIP-ova mice. First, we will analyze the roles of CD28 and ICOS in regulation of Tc cell activation. We will transfer ICOS+/+ and ICOS-/- OT-I cells into RIP-mOva transgenic mice sufficient or deficient in the B7.1 and B7.2 genes, and their activation and tolerance will be examined. Secondly, we will examine the roles of PDL2, B7-H3 and B7S1 in regulation of Tc cell tolerance. We will transfer OT-I T cells into RIP-mOva mice with or without treatment with anti-PDL2, BT-H3 or B7S1 blocking antibodies and the activation or tolerance of the transferred cells wilt be examined. This study will advance our understanding on costimulatory regulation of Tc activation and tolerance, and may likely to suggest means to modulate immune tolerance to tissue antigens.