Specificity and Function of CD25+ Regulatory T Cells

描述（由申请人提供）：该项目的目标是使用一个特征良好的模型系统来定义控制CD4+CD25+Foxp3+调节性T （Treg）细胞形成和活性的过程。该提案将利用现有的转基因小鼠谱系，在多种启动子（HA Tg小鼠）和/或HA特异性T细胞受体的控制下表达流感病毒血凝素（HA），这些T细胞受体对HA具有不同的亲和力和特异性（TCR Tg小鼠）。通过分析双转基因小鼠共表达HA特异性TCRs和新自我HA肽（TCRxHA Tg小鼠），我们发现，与HA衍生肽的高度特异性相互作用可以诱导胸腺细胞选择成为Treg细胞，从而在体外抑制常规CD4+ T （Tconv）细胞反应，并在体内修饰免疫反应。我们已经证明，这些Treg细胞的形成对不同HA Tg谱系中HA表达量的变化高度敏感，并且在这些谱系之一（指定的HACII小鼠）中，抗原呈递细胞选择性地表达HA诱导TCRxHACII小鼠炎症性关节炎的自发发展，尽管存在抗原特异性Treg细胞。我们将使用这个独特的模型系统来研究TCR特异性如何指导Treg细胞的形成，并确定Treg细胞调节抗自身和抗病毒免疫反应的能力。在目标1中，我们将研究自肽的TCR识别如何塑造Treg库的形成。我们将调节TCR对自身肽的反应性，并确定对TCRxHA Tg小鼠胸腺Treg细胞发育的影响，并将使用过继性转移方法来检测不同条件下HA Tg小鼠外周血Treg细胞的发育。在目标2中，我们将研究Treg特异性对自身肽如何影响抗病毒免疫。我们将分析来自TCRxHA Tg小鼠的Treg细胞调节流感病毒抗体反应的能力，因为它们具有不同程度的交叉反应性，并检测不共表达TCR转基因的HA Tg小鼠的病毒特异性CD4+ Treg和Tconv细胞的频率。在Aim 3中，我们将确定TCR特异性如何影响Treg细胞预防自身免疫性关节炎的能力。我们将在患关节炎前的TCRxHACII小鼠中要么消耗Treg细胞，要么添加与HA具有不同程度反应性的Treg细胞，并确定对伴随关节炎发展的细胞过程的影响。我们还将分析转移到HACII或TS1xHACII小鼠后，对HA具有不同程度反应性的Treg细胞的扩增和分化。这些研究将为免疫库形成和耐受性的机制提供基本的见解。它们将增强我们对免疫调节在抗病毒免疫中所起作用的理解，以及它的失败如何导致自身免疫，并将增强Treg细胞在诊断治疗环境中的利用能力。

DESCRIPTION (provided by applicant): This project's goal is to use a well-characterized model system to define processes governing the formation and activity of CD4+CD25+Foxp3+ regulatory T (Treg) cells. The proposal will make use of existing lineages of transgenic mice expressing the influenza virus hemagglutinin (HA) under the control of a variety of promoters (HA Tg mice) and/or HA-specific T cell receptors with varying affinities and specificities for the HA (TCR Tg mice). By analyzing double transgenic mice co-expressing HA-specific TCRs and neo-self HA peptides (TCRxHA Tg mice), we have shown that highly specific interactions with HA-derived peptides can induce thymocytes to undergo selection to become Treg cells that suppress conventional CD4+ T (Tconv) cell responses in vitro, and can modify immune responses in vivo. We have shown that the formation of these Treg cells is highly sensitive to variations in the amount of the HA that is expressed in different HA Tg lineages, and that expression of HA selectively by antigen presenting cells in one of these lineages (designated HACII mice) induces the spontaneous development of inflammatory arthritis in TCRxHACII mice despite the presence of antigen-specific Treg cells. We will use this unique model system to examine how TCR specificity directs Treg cell formation and determines the capacity of Treg cells to modulate anti-self and anti-viral immune responses. In Aim 1 we will examine how TCR recognition of self-peptides shapes Treg repertoire formation. We will modulate the reactivity of the TCR for self-peptides and determine the effects on thymic Treg cell development in TCRxHA Tg mice, and will use adoptive transfer approaches to examine the development of Treg cells in the periphery of HA Tg mice under various conditions. In Aim 2 we will examine how Treg specificity for self-peptides shapes anti-viral immunity. We will analyze the ability of Treg cells from TCRxHA Tg mice to modulate antibody responses to influenza viruses with which they possess varying degrees of crossreactivity, and examine HA Tg mice that do not co-express TCR transgenes for their frequencies of virus- specific CD4+ Treg and Tconv cells. In Aim 3 we will determine how TCR specificity impacts the ability of Treg cells to prevent autoimmune arthritis. We will either deplete Treg cells, or add Treg cells with varying degrees of reactivity with the HA to pre-arthritic TCRxHACII mice, and determine the effects on cellular processes that accompany arthritis development. We will also analyze the expansion and differentiation of Treg cells with varying degrees of reactivity for the HA following transfer into HACII or TS1xHACII mice. These studies will provide fundamental insights into the mechanisms of immune repertoire formation and tolerance. They will enhance our understanding of the role immune regulation plays in anti-viral immunity and how its failure can contribute to autoimmunity, and will enhance the ability of Treg cells to b exploit in diagnostic therapeutic settings. PUBLIC HEALTH RELEVANCE: Regulatory T cells play an vital role in preventing the immune system from mounting harmful responses to the body's cells and tissues, such as can occur in autoimmune diseases. These cells can also modify the activity of the immune system in settings such as infection, transplantation and cancer. This proposal uses genetically-modified mice to analyze mechanisms and cellular processes than govern the development and activity of regulatory T cells, and to develop novel insights into regulatory T cell biology that will facilitate their application for diagnosis and therapy of human diseases.