Exploring Regulatory T Cell Dysfunction in a Murine Model of Colitis

描述（由申请人提供）：本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小鼠模型的建立促进了对IBD发病机制的研究。尽管事实上许多IBD的鼠模型是由已知影响白细胞功能的单一蛋白质的缺陷引起的，但在这些模型中负责疾病发病机制的特异性自身反应性和/或调节性细胞群仍然未知。我们最近建立了一个IBD小鼠模型，该模型是由Wiskott-Aldrich综合征蛋白（WASP）的靶向破坏引起的。WASP仅在造血细胞中表达，并且是调节细胞表面受体信号至细胞骨架的信号传导分子。这种蛋白质的缺失导致罕见的X连锁原发性免疫缺陷，并以其命名。自身免疫通常与这种免疫缺陷有关，高达10%的患者会发展为IBD样疾病。我们的实验室最近表明，100%的WASP KO（WKO）小鼠也会发生结肠炎。遗传和过继转移研究表明，淋巴细胞是必不可少的，CD 4+淋巴细胞足以促进结肠炎的发展。与具有Th 1偏好的IBD的大多数鼠模型相反，我们已经证明了固有层（LP）淋巴细胞和组织中的Th 2细胞因子偏斜（IL-4和IL-13升高）。事实上，IL-4是结肠炎发展所必需的，至少是部分必需的。也许，最有趣的是，我们最近发现WKO动物中调节性T细胞的发育和功能显着减少。我们的总体假设是，WKO小鼠中的结肠炎由导致Treg功能障碍的内在Treg功能障碍以及CD 4 + T细胞/APC群体内的外在信号传导/细胞因子异常引起。在这个提议中，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旨在揭示导致WKO小鼠中Treg异常发育和功能障碍的机制（发育，迁移和细胞-细胞接触）。目的2旨在评估先天性免疫细胞中WASP缺乏对T细胞生成和功能的影响。目的3旨在确定WASP依赖性T细胞受体（TCR）信号传导和异常细胞因子分泌对Treg功能障碍的作用。该提案的总体目标是进一步了解WKO小鼠中结肠炎的机制，该机制独特地与深刻的调节性T细胞缺陷和Th 2细胞因子偏斜相关，并利用具有独特的人类相关性的结肠炎小鼠模型。我们的驱动前提是，这些知识不仅有助于理解和治疗衰弱的自身免疫（和IBD样疾病），这是人类免疫缺陷的特征，但也将有助于我们理解粘膜免疫调节一般和炎症性肠病的分子基础。公共卫生相关性：本提案的总体目标是进一步了解Wiskott Aldrich综合征蛋白敲除小鼠中的调节性T细胞缺陷和结肠炎机制，并利用也具有人类相关性的结肠炎模型。

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.