Low affinity CD8+ T cells in diabetes

胸腺和外周缺失是消除潜在自身反应性T细胞的重要保障。然而，为了最大限度地提高T细胞库的多样性，删除是一种很少使用的机制，并且保留给那些表达对自身表位具有相对高亲和力的tcr的T细胞。由于这种相当保守的方法，许多对自身表位具有特异性的T细胞持续存在。这一提议的主要假设是这些原本无害的T细胞在自身免疫性糖尿病中成为重要的效应细胞。我们的目标是使用一种转基因模型来验证这一假设，在该模型中，流感血凝素（HA）在胰岛中唯一表达（in -HA），而TCR转基因小鼠系表达来自HA特异性CD8+ T细胞克隆的TCR。（克隆1tcr）。重要的是，该克隆来源于具有HA耐受性的Ins-HA小鼠，与来自常规小鼠的HA特异性CTL的TCR相比，TCR对HA的亲和力相对较低。一些可能证明克隆1 T细胞自身免疫的实验参数将在本研究中进行评估，包括在胰岛局部促进炎症环境的条件，例如在NOD小鼠中发生的情况，或通过使用HA特异性、活化的CD4+ T细胞或柯萨奇病毒在非糖尿病易感性小鼠中创造炎症环境。还需要评估的假设是，通过使用表达靶抗原的DNA疫苗从库中消除这种潜在的自身免疫性CD8+ T细胞，可能会防止NOD小鼠的自身免疫。在这种情况下，将评估两种不同的抗原，内源性β细胞抗原GAD65和HA转基因产物。

Thymic and peripheral deletion represent important safeguards to eliminate potentially autoreactive T cells. However, in the interest of maximizing diversity in the T cell repertoire, deletion is a mechanisms used sparingly and reserved for those T cells expressing TCRs with relatively high affinity for self-epitopes. As a result of this rather conservative approach, many T cells with specificity for self-epitopes persist. The main hypothesis of this proposal is that these otherwise innocuous T cells become important effector cells in autoimmune diabetes. Our goal is to test this hypothesis using a transgenic model in which the influenza hemagglutinin (HA), is expressed uniquely in the pancreatic islets (Ins-HA) and a TCR transgenic murine line expressing a TCR from a HA specific CD8+ T cell clone. (Clone 1 TCR). Importantly, this clone was derived from an Ins-HA mouse that demonstrates tolerance to HA and the TCR demonstrates relatively low affinity for HA as compared with TCRs from HA specific CTL from conventional mice. Some of the experimental parameters that may prove autoimmunity by the Clone 1 T cells that will be evaluated in this study include conditions that promote an inflammatory environment locally in the islets, such as occurs in NOD mice, or by creating an inflammatory environment in non- diabetes prone mice using HA specific, activated CD4+ T cells, or Coxsackie virus. Also to be evaluated is the hypothesis that eliminating such potentially autoimmune CD8+ T cells from the repertoire, by the use of a DNA vaccine expressing the target antigen, may prevent autoimmunity in NOD mice. Two different antigens will be evaluated in this context, an endogenous beta cell antigen, GAD65, and the HA transgene product.