Exploring Regulatory T Cell Dysfunction in a Murine Model of Colitis

描述(申请人提供)：这个项目的总体目标是进一步了解粘膜免疫系统和导致人类炎症性肠病(IBD)发病机制的缺陷。许多IBD小鼠模型的建立为研究IBD发病的基本机制提供了便利。尽管许多IBD小鼠模型是由一种已知的影响白细胞功能的单一蛋白缺陷引起的，但在这些模型中，负责疾病发病机制的特定自身反应和/或调节细胞群仍不清楚。我们最近建立了一个IBD的小鼠模型，这是由于Wiskott-Aldrich综合征蛋白(WASP)的靶向中断造成的。黄蜂蛋白只在造血细胞中表达，是一种信号分子，调节细胞表面受体信号到细胞骨架。这种蛋白的异常导致了罕见的X连锁初级免疫缺陷，以它的名字命名。自身免疫通常与这种免疫缺陷有关，高达10%的患者会患上类似IBD的疾病。我们的实验室最近表明，100%的WASP KO(WKO)小鼠也会患结肠炎。遗传和过继转移研究表明，淋巴细胞对于结肠炎的发展是必不可少的，而CD4+淋巴细胞是足够的。与大多数具有Th1偏向的IBD小鼠模型不同，我们在固有层(LP)淋巴细胞和组织中发现了Th2细胞因子的偏斜(IL-4和IL-13升高)。事实上，结肠炎的发生至少在一定程度上需要IL-4。也许，最有趣的是，我们最近发现，在WKO动物中，调节性T细胞的发育和功能明显减少。我们的总体假设是，WKO小鼠的结肠炎既是内在Treg功能障碍的结果，也是导致Treg功能障碍的CD4+T细胞/APC群体中外部信号/细胞因子异常的结果。在这项建议中，我们试图确定WKO小鼠结肠炎发展和自身免疫的细胞和分子基础。目的1试图揭示导致WKO小鼠Treg异常发育和功能障碍的机制(S)(发育、迁移和细胞-细胞接触)。目的2探讨先天免疫细胞中WASP缺陷对Tregs生成和功能的影响。目的研究WASP依赖的T细胞受体(TCR)信号转导和细胞因子分泌异常在Treg功能障碍中的作用。这项建议的总体目标是促进我们对WKO小鼠结肠炎机制的理解，该机制与深刻的调节性T细胞缺陷和Th2细胞因子扭曲独特相关，并利用唯一与人类相关的结肠炎小鼠模型。我们的主要前提是，这些知识不仅有助于理解和治疗以人类免疫缺陷为特征的衰弱的自身免疫(和IBD样疾病)，而且还有助于我们总体上了解粘膜免疫调节和炎症性肠病的分子基础。公共卫生相关性：这项建议的总体目标是加深我们对Wiskott Aldrich综合征蛋白敲除小鼠中调节性T细胞缺陷和结肠炎机制的理解，并利用也与人类相关的结肠炎模型。

DESCRIPTION (provided by applicant): The overall goal of this project is to gain further understanding of the mucosal immune system and the defects that contribute to the pathogenesis of human inflammatory bowel disease (IBD). The generation of a number of murine models of IBD has facilitated investigation into the basic mechanisms underlying IBD pathogenesis. Despite the fact that many murine models of IBD result from a defect in a single protein known to affect leukocyte function, the specific auto-reactive and/or regulatory cell population responsible for disease pathogenesis in these models remains unknown. We recently generated a mouse model of IBD that results from the targeted disruption of the Wiskott-Aldrich syndrome protein (WASP). WASP is expressed solely in hematopoietic cells and is a signaling molecule that regulates cell surface receptor signals to the cytoskeleton. Abnormalities in this protein lead to the rare X-linked primary immunodeficiency that carries its name. Autoimmunity is commonly associated with this immunodeficiency, and up to 10 percent of patients develop an IBD-like illness. Our lab has recently shown that 100% of WASP KO (WKO) mice also develop colitis. Genetic and adoptive transfer studies have shown that lymphocytes are essential and CD4+ lymphocytes are sufficient for colitis development. In contrast with most murine models of IBD that have a Th1 bias, we have demonstrated a Th2 cytokine skewing (with elevated IL-4 and IL-13) in lamina propria (LP) lymphocytes and in tissues. Indeed, IL-4 is required, at least in part, for colitis development. Perhaps, most interestingly, we have recently shown that there is marked reduction in the development and function of regulatory T cells in WKO animals. Our overall hypothesis is that the colitis in WKO mice results from both intrinsic Treg dysfunction as well as extrinsic signaling/cytokine abnormalities within the CD4+ T cell/APC population that results in Treg dysfunction. In this proposal we seek to determine the cellular and molecular basis for colitis development and autoimmunity in WKO mice. Aim 1 seeks to uncover the mechanism(s) (development, migration, and cell-cell contacts) that are responsible for the aberrant Treg development and dysfunction in WKO mice. Aim 2 seeks to assess the impact of WASP deficiency in innate immune cells on the generation and function of Tregs. Aim 3 seeks to determine the role of WASP-dependant T cell receptor (TCR) signaling and aberrant cytokine secretion on Treg dysfunction. The overall goal of this proposal is to further our understanding of the mechanism of colitis in WKO mice that is uniquely associated with both profound regulatory T cell defects and Th2 cytokine skewing and to take advantage of a murine model of colitis that uniquely has a human correlate. Our driving premise is that such knowledge will not only aid in the understanding and treatment of the debilitating autoimmunity (and IBD-like illness) that characterizes the human immunodeficiency but will also aid in our understanding of mucosal immune regulation in general and the molecular underpinnings of inflammatory bowel disease. PUBLIC HEALTH RELEVANCE: The overall goal of this proposal is to further our understanding of the regulatory T cell defects and the mechanism of colitis in Wiskott Aldrich Syndrome protein knock-out mice and to take advantage of a model of colitis that also has a human correlate.