Specificity and Function of CD25+ Regulatory T Cells

描述(由申请人提供)：这个项目的目标是使用一个特性良好的模型系统来定义管理CD4+CD25+Foxp3+调节性T细胞(Treg)的形成和活性的过程。该提案将利用现有的转基因小鼠在多种启动子(HA TG小鼠)和/或HA特异性T细胞受体(TCR TG小鼠)的控制下表达流感病毒血凝素(HA)。通过分析共表达HA特异性TCRs和新自身HA多肽的双转基因小鼠(TCRxHATG小鼠)，我们发现与HA衍生多肽的高度特异性相互作用可以诱导胸腺细胞经过选择成为Treg细胞，在体外抑制常规的CD4+T(Tconv)细胞反应，并在体内改变免疫反应。我们已经证明，这些Treg细胞的形成对不同HA TG谱系中表达的HA数量的变化高度敏感，并且这些谱系之一(指定为HACII小鼠)中的抗原提呈细胞选择性地表达HA可以诱导TCRxHACII小鼠炎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，我们将研究自体肽的TCR识别如何塑造Treg谱系的形成。我们将调节TCR对自体肽的反应性，并确定其对TCRxHA TG小鼠胸腺Treg细胞发育的影响，并将使用过继转移方法来检测不同条件下HA TG小鼠外周Treg细胞的发育。在目标2中，我们将研究自体肽的Treg特异性如何形成抗病毒免疫。我们将分析来自TCRxHA TG小鼠的Treg细胞调节对流感病毒的抗体反应的能力，它们与流感病毒具有不同程度的交叉反应，并检查不共表达TCR转基因的HA TG小鼠的病毒特异性CD4+Treg和Tconv细胞的频率。在目标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。我们将耗尽Treg细胞，或将与HA具有不同程度反应性的Treg细胞添加到关节炎前期TCRxHACII小鼠中，并确定对伴随关节炎发展的细胞过程的影响。我们还将分析具有不同程度HA反应性的Treg细胞在转移到HACII或TS1xHACII小鼠后的扩增和分化情况。这些研究将为免疫谱系的形成和耐受的机制提供基本的见解。它们将加深我们对免疫调节在抗病毒免疫中的作用以及免疫调节失败如何导致自身免疫的理解，并将增强Treg细胞在诊断治疗环境中最佳利用的能力。 公共卫生相关性：调节性T细胞在防止免疫系统对人体细胞和组织产生有害反应方面发挥着至关重要的作用，这种反应可能发生在自身免疫性疾病中。这些细胞还可以在感染、移植和癌症等环境中改变免疫系统的活动。这项建议使用转基因小鼠来分析机制和细胞过程，以控制调节性T细胞的发展和活动，并对调节性T细胞生物学发展新的见解，这将促进它们在人类疾病诊断和治疗中的应用。

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.