Mechanisms of Peripheral Induction of T-cell Tolerance

描述（由申请人提供）：在次级淋巴器官（外周）中增强T细胞对自身抗原（自身抗原）耐受性的机制对于预防自身免疫性疾病的发展至关重要，但也可能限制对自身抗原（如肿瘤疫苗）或外来抗原（如病原体疫苗）的预期应答的诱导。关于介导外周T细胞耐受性的机制已经知道很多，但仍然存在许多基本问题，并且对这些过程的理解将导致操纵耐受性以预防或治疗自身免疫性疾病的能力增强。 该计划的重点是通过检查CD4和CD8 T细胞耐受性来解决这些问题 在细胞和分子水平的机制。该计划包括四个项目，都侧重于 自身免疫性疾病模型中对自身抗原的耐受性： 项目1。体内外周耐受性分析（M。詹金斯） 项目2.无能性T细胞的功能表征（D.穆勒） 项目3。多克隆T细胞群中的自身反应性（K. Hogquist） 项目4。自身抗原诱导的CD8 T细胞无反应性的机制（M.梅舍尔） 总体计划目标是获得新的见解的基本机制，导致T细胞 耐受性，并确定这些机制如何以及在何处发挥作用，以加强小鼠和人类对自身抗原的耐受性。每个项目都将应用创新技术来解决这些问题。特别值得注意的是，根据该计划开发的新技术将允许在以前不可能的水平上分析自我反应性人类T细胞，并可能为新的临床试验奠定基础。我们预计，通过拟议的研究获得的耐受性诱导机制方面的新见解将导致新的策略，促进自身免疫性疾病的耐受性或避免在保护性或治疗性疫苗接种耐受性。 相关性：每个项目都使用自身免疫性疾病模型来研究T细胞中对自身抗原的外周耐受诱导的细胞和分子机制。项目之间的许多互动将为实现总体计划目标提供协同作用。行政核心将提供预算和科学监督，核心B（自身免疫小鼠核心）将支持所有四个项目。 项目1：体内外周耐受性分析 项目负责人：Marc Jenkins 描述（由申请人提供）：尽管产生表达自身肽（p）特异性T细胞受体（TCR）的CD4+ T细胞：主要组织相容性复合物II（MHCII）配体，但大多数人不会患有自身免疫。在TCR转基因小鼠模型中的许多研究表明，这是因为这些CD4+ T细胞在胸腺中缺失或在次级淋巴器官中分化为无反应性或抑制性调节性T（Treg）细胞。然而，这些机制对所有自身抗原耐受性的相对贡献尚未达成共识。因此，基本问题仍然有待回答，如胸腺缺失的效率如何，无反应性T细胞是否存在，Treg细胞库是否真的富含自身p：MHCII特异性细胞，以及这些机制中的哪一种在自身免疫过程中失败？我们将回答这些问题，通过研究多克隆内源性CD4+ T细胞特异性自身p：MHCII配体使用敏感的p：MHCII四聚体为基础的细胞富集方法。在小鼠中，我们将确定是否T细胞表达TCR与普遍存在的自身p：MHCII配体的最高亲和力被删除，以及是否一些T细胞特异性p：MHCII配体衍生自外周组织特异性蛋白表达在胸腺的自身免疫调节（AIRE）的控制下逃脱删除，但成为无反应性或分化成Treg细胞在次级淋巴器官。我们将尝试通过直接离体跟踪血糖正常或1型糖尿病患者的胰岛素或谷氨酸脱羧酶p：MHCII特异性CD4+ T细胞的数量、功能和表型来证实这些假设。如果成功，我们将了解胸腺克隆缺失的效率，无反应性是否作为耐受机制存在，以及自身反应性T细胞群是否富含Treg细胞，所有这些都在正常的多克隆库中。这些实验可以为未来的临床试验奠定基础，以确定基于自体p：MHCII四聚体的细胞富集是否可以用作糖尿病早期诊断或监测免疫治疗疗效的工具。 相关性：该项目的重点是防止CD4+ T细胞引起自身免疫的免疫耐受机制。它将采用创新的T细胞跟踪技术，以弥合小鼠模型中的机制研究与应用于人类免疫系统之间的差距。本申请中描述的方法可能会导致诊断糖尿病和监测免疫治疗的新方法。

DESCRIPTION (provided by applicant): Mechanisms that enforce T tolerance to self-antigens (self-Ags) in the secondary lymphoid organs (periphery) are critical for preventing development of autoimmune diseases, but can also limit the induction of desirable responses to self-Ags, as in the case of tumor vaccines, or to foreign Ags, as in the case of vaccines for pathogens. Much is known about the mechanisms that mediate peripheral T cell tolerance, but many fundamental questions remain, and developing an increased understanding of these processes will lead to an enhanced ability to manipulate tolerance for prevention or treatment of autoimmune diseases. This Program focuses on addressing these questions by examining CD4 and CD8 T cell tolerance mechanisms at the cellular and molecular levels. The Program includes four projects that all focus on tolerance to self-antigens in autoimmune disease models: Project 1. Analysis of peripheral tolerance in vivo (M. Jenkins) Project 2. Functional characterization of anergic T cells (D. Mueller) Project 3. Self reactivity in polyclonal T cell populations (K. Hogquist) Project 4. Mechanisms of self-Ag-induced non-responsiveness in CD8 T cells (M. Mescher) The overall Program goals are to gain new insights into fundamental mechanisms that lead to T cell tolerance and determine how and where these mechanisms act to enforce tolerance to self-antigens in mice and humans. Each project will apply innovative technologies to address these questions. Of particular note, new technology developed under this Program will allow analysis of self-reactive human T cells at a level not previously possible, and is likely to set the stage fr novel clinical trials. We anticipate that novel insights into mechanistic aspects of tolerance induction gained through the proposed studies will lead to new strategies for promoting tolerance in autoimmune diseases or avoiding tolerance during protective or therapeutic vaccination. RELEVANCE: Each project uses autoimmune disease models to study the cellular and molecular mechanisms for peripheral tolerance induction to self-antigens in T cells. Numerous interactions between the projects will provide synergy in achieving the overall Program goals. An Administrative Core will provide budgetary and scientific oversight and Core B (Autoimmune Mouse Core) will support all four of the projects. Project 1: Analysis of peripheral tolerance in vivo Project Leader: Marc Jenkins DESCRIPTION (provided by applicant): Most people do not suffer from autoimmunity despite the production of CD4+ T cells expressing T cell receptors (TCR) specific for self peptide (p):major histocompatibility complex II (MHCII) ligands. Many studies in TCR transgenic mouse models have shown that this is the case because these CD4+ T cells are deleted in the thymus or differentiate into anergic or suppressive regulatory T (Treg) cells in secondary lymphoid organs. Nevertheless, consensus on the relative contributions of these mechanisms to tolerance to all self antigens has not been reached. Fundamental questions therefore remain to be answered such as how efficient is thymic deletion, do anergic T cells exist, is the Treg cell repertoire really enriched for self p:MHCIl-specific cells, and which of these mechanisms fails during autoimmunity? We will answer these questions by studying polyclonal endogenous CD4+ T cells specific for self p:MHCII ligands using a sensitive p:MHCII tetramer-based cell enrichment method. In mice, we will determine whether T cells expressing TCRs with the highest affinities for ubiquitous self p:MHCII ligands are deleted, and whether some T cells specific for p:MHCII ligands derived from peripheral tissue-specific proteins expressed in the thymus under the control of the Autoimmune Regulator (AIRE) escape deletion but become anergic or differentiate into Treg cells in the secondary lymphoid organs. We will attempt to confirm these hypotheses in humans by direct ex vivo tracking of the number, function, and phenotype of insulin or glutamic acid decarboxylase p:MHCII-specific CD4+ T cells from normoglycemic or type 1 diabetic people. If successful, we will have learned how efficient thymic clonal deletion is, whether anergy exists as a tolerance mechanism, and if self-reactive T cell populations are enriched for Treg cells, all within normal polyclonal repertoires. These experiments could set the stage for future clinical trials to determine if self p:MHCII tetramer-based cell enrichment can be used as a tool for early diagnosis of diabetes or to monitor the efficacy of immunotherapy. RELEVANCE: This project focuses on the mechanisms of immune tolerance that prevent CD4+ T cells from causing autoimmunity. It will employ innovative T cell tracking technology to bridge the gap between mechanistic studies in mouse models and application to the human immune system. The approach described in this application could lead to new methods for diagnosing diabetes and monitoring immunotherapy.