Specificity and Function of CD25+ Regulatory T Cells

描述（由申请人提供）：本项目的目标是使用充分表征的模型系统来定义控制CD 4 + CD 25 + Foxp 3+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，这些转基因小鼠在多种启动子（HA Tg小鼠）和/或对HA具有不同亲和力和特异性的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TCR和新自身HA肽的双转基因小鼠（TCRxHA Tg小鼠），我们已经表明，与HA衍生肽的高度特异性相互作用可以诱导胸腺细胞经历选择，成为抑制体外常规CD 4 + T（Tconv）细胞应答的Treg细胞，并且可以改变体内免疫应答。我们已经表明，这些Treg细胞的形成对在不同HA Tg谱系中表达的HA的量的变化高度敏感，并且尽管存在抗原特异性Treg细胞，但通过这些谱系之一（指定为HACII小鼠）中的抗原呈递细胞选择性地表达HA诱导TCR xHACII小鼠中炎性关节炎的自发发展。我们将使用这种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应答的能力。在目标1中，我们将研究TCR对自身肽的识别如何影响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小鼠中胸腺Treg细胞发育的影响，并将使用过继转移方法来检查各种条件下HA Tg小鼠外周中Treg细胞的发育。在目标2中，我们将研究Treg对自身肽的特异性如何塑造抗病毒免疫。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应答的能力，它们与流感病毒具有不同程度的交叉反应性，并检查不共表达TCR转基因的HA Tg小鼠的病毒特异性CD 4 + 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TCRxHACII小鼠，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Treg细胞在转移到HACII或TS 1xHACII小鼠中后对HA具有不同程度反应性的扩增和分化。这些研究将为免疫库形成和耐受机制提供基本见解。它们将增强我们对免疫调节在抗病毒免疫中的作用以及其失效如何有助于自身免疫的理解，并将增强Treg细胞在诊断治疗环境中利用B的能力。

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.