CD40-Induced TCR Revision: A Mechanism for Autoimmunity

描述(由申请人提供)：本申请的目标是解决CD40 T细胞的发育，CD40在T细胞受体(TCR)修订中所起的作用，以及诱导TCR修订如何影响自身免疫。CD40在包括1型糖尿病(T1D)在内的自身免疫性疾病中具有直接作用。我们发现，一个独特的效应T细胞亚群，被描述为CD4loCD40，在T1 D是高致病性的。在NOD小鼠中，CD40存在于糖尿病T细胞克隆上，原代CD4loCD40 T细胞在胰岛素炎的同时扩张。重要的是，CD4loCD40 T细胞很容易将T1D转移给NOD.SCID接受者。CD40在机制上诱导T细胞RAG1/RAG2重组机制。在诱导之后，TCR修改发生，诱导TCR表达的改变。一些修改过的初级T细胞被发现是高致病性的。然而，CD40诱导的TCR修订可能是已建立的糖尿病原性T细胞克隆的一种功能耐受机制。具体地说，CD40与糖尿病T细胞克隆BDC2.5的结合严重破坏了该克隆的疾病转移能力。我们发现，在3周龄的NOD小鼠中，阻断CD40-CD154(CD40的配体)相互作用不仅可以防止T1D的发生，而且可以防止CD4loCD40自身侵袭性细胞的扩张。在这项应用中，我们将探索CD40如何影响独特的T细胞群。我们的假设是TCR的改变直接影响T细胞的耐受性。具体目标#1：CD4loCD40 T细胞是构成一个独特的T细胞亚群，还是代表T细胞内的一种瞬时激活状态？如果在T细胞上诱导CD40，与固有的CD40 T细胞亚群相比，这些T细胞有什么不同？我们计划进行实验，以解决这一核心问题。具体目标2：CD40参与如何影响CD4loCD40 T细胞的TCR修订？自身免疫性疾病和非自身免疫性疾病对CD40参与的反应是否存在差异？我们将探索RAG1和RAG2的诱导，TCR修订的动力学，以及自身免疫和非自身免疫小鼠中不同来源的CD154如何影响这一过程。具体目标#3：CD40参与如何影响T细胞抗原特异性？我们将使用体外和体内模型来探索诱导的TCR修改如何影响T细胞抗原特异性。这些拟议的研究不仅涉及潜在的自身侵袭性T细胞的发展，而且将提供关于诱导的TCR修订是致病的还是耐受的重要信息。

DESCRIPTION (provided by applicant): The goals of this application are to address the development of CD40+ T cells, the role that CD40 plays in T cell receptor (TCR) revision and how induced TCR revision impacts autoimmunity. CD40 has a direct role in autoimmune diseases including type 1 diabetes (T1D). We discovered that a unique subset of effector T cells, described as CD4loCD40+, are highly pathogenic in T1 D. CD40 is present on diabetogenic T cell clones and primary CD4loCD40+ T cells expand concurrently with insulitis in NOD mice. Importantly, CD4loCD40+ T cells readily transfer T1D to NOD.scid recipients. Mechanistically, CD40 induces the RAG1/RAG2 recombination machinery in T cells. Following that induction, TCR revision, induced alteration of TCR expression, occurs. Some revised primary T cells were found to be highly pathogenic. However, CD40 induced TCR revision could serve as a functional tolerance mechanism of established diabetogenic T cell clones. Specifically, CD40 engaging the diabetogenic T cell clone BDC2.5 severely ablated disease transfer ability of the clone. We showed that blocking CD40 - CD154 (the ligand for CD40) interaction in NOD mice at 3-weeks of age prevents not only T1D onset, but prevents expansion of CD4loCD40+, autoaggressive cells. In this application we will explore how CD40 affects the unique T cell population. Our hypothesis is that TCR revision directly impacts T cell tolerance. Specific Aim #1: Do CD4loCD40+ T cells comprise a unique T cell subset or represent a transient activation state within T cells? If CD40 is induced on T cells are there differences in those T cells compared to the intrinsic CD40 T cell subset? We plan experiments to address this central concern. Specific Aim #2: How does CD40 engagement affect TCR revision in CD4loCD40+ T cells? Are there differences in response to CD40 engagement between autoimmune and non-autoimmune conditions? We will explore RAG1 and RAG2 induction, kinetics of TCR revision and how different sources of CD154 in autoimmune versus non-autoimmune mice affect this process. Specific Aim #3: How does CD40 engagement affect T cell antigen specificity? We will explore how induced TCR revision affects T cell antigen specificity using in vitro and in vivo models. These proposed studies address not only the development of potential autoaggressive T cells but will provide important information as to whether induced TCR revision is pathogenic or tolerogenic.