ANTIGEN HANDLING AND CYTOKINE PHENOTYPE REGULATION IN NORMAL AND INFLAMED COLON

炎症性肠病（IBD）的发病机制涉及免疫、遗传和环境因素之间的复杂相互作用。来自越来越多的IBD小鼠模型的证据支持失调的CD 4 T细胞对肠道细菌植物群的应答作为常见疾病机制的中心作用。虽然这些模型已经将注意力引向作为疾病介质的特定T细胞亚群和细胞因子以及驻留在粘膜免疫组织（特别是结肠）中的CD 4 T细胞。引发和维持慢性肠道炎症的特异性抗原和细菌种群尚不清楚。类似地，正常和失调的CD 4 T细胞群的抗原特异性和表型是未知的或表征不佳。该提案将使用抗原特异性模型来研究克隆CD 4 T细胞群体与其在肠道中的同源抗原之间的相互作用，从而检查慢性结肠炎症的起始和进展。充分表征的卵清蛋白（OVA）特异性D011.10TCR转基因小鼠模型将用于描述CD 4 T细胞识别和应答结肠中游离或细菌相关的OVA的机制，并确定该应答的特异性破坏如何导致结肠炎。我们假设盲肠和近端结肠中细菌植物群的周转产生三种一般类型的抗原：由垂死生物体释放的游离、胞质和周质抗原;细胞膜或细胞壁相关抗原：由垂死生物体释放的游离、胞质和周质抗原;由垂死生物体释放的细胞膜或细胞壁相关抗原，以及完整的活生物体。这些不同形式的细菌抗原在结肠淋巴滤泡或更远端的免疫组织中的摄取，驱动不同谱系的CD 4 T细胞的分化。游离细菌抗原是有利于调节型（例如Th 1）细胞发育的耐受原，而膜相关抗原和活生物体，因为它们是具有炎性特性的颗粒抗原，所以优先诱导促炎效应CD 4细胞（例如Th 1细胞）。肠淋巴组织处理的抗原负荷的混合性质刺激维持稳态的促炎和抗炎CD 4 T细胞表型的分化。在第一个目标中，我们将测试的假设，在体内发展的Tr 1型调节性T细胞的识别诱导的游离抗原，而导致结肠炎的促炎效应细胞的发展需要识别的细菌相关抗原。在第二个目标中，我们将检验以下假设：在缺乏调节性CD 4 T细胞群的情况下，效应CD 4 T细胞诱导由细菌相关抗原驱动的抗原特异性结肠炎。

The pathogenesis of inflammatory of inflammatory bowel disease (IBD) involves complex interactions among immune, genetic, and environmental factors. Evidence from a growing number of mouse models of IBD support a central role for disregulated CD4 T cell responses to the enteric bacterial flora as a common disease mechanism. While these models have directed attention to specific T cell subpopulations and cytokines as mediators of disease and CD4 T cells resident in mucosal immune tissues, particular the colon. The specific antigen(s) and bacterial populations that initiate and sustain chromic intestinal inflammation are unknown. Similarly, the antigenic specificity and phenotypes of normal and disregulated CD4 T cell population are unknown or poorly characterized. This proposal will examine the initiation and progression of chronic colonic inflammation using an antigen-specific model for study of interactions between clonal CD4 T cell populations with their cognate antigen in the intestine. The well- characterized, ovalbumin (OVA)-specific DO11.10 TCR transgenic mouse model will be used to delineate the mechanism of CD4 T cell recognition and response to free or bacterially associated OVA in the colon, and to determine how specific disruptions of this response lead to colitis. We postulate that turnover of the bacterial flora in the cecum and proximal colon generate three general types of antigens: free, cytosolic and periplasmic antigens released by dying organisms; cell membrane or cell wall associated antigens: free, cytosolic and periplasmic antigens released by dying organisms; cell membrane or cell wall associated antigens released by dying organisms, and intact, viable organisms. Uptake of these different forms of bacterial antigens in the colonic lymphoid follicles, or more distal immune tissues, drive differentiation of distinct lineages of CD4 T cells. Free bacterial antigens are toleragens that favor development of regulatory type (e.g. Th1) cells, whereas membrane associated antigens and live organisms, because they are particulate antigens with phlogistic properties, preferentially induce pro-inflammatory effector CD4 cells (e.g. Th1 cells). It is the mixed nature of the antigenic load handled by the intestinal lymphoid tissues that stimulates differentiation of pro- and anti-inflammatory CD4 T cell phenotypes that maintain homeostasis. In the first aim, we will test the hypothesis that in vivo development of Tr1-type regulatory T cells is induced by recognition of free antigen whereas development of pro-inflammatory effector cells that cause colitis requires recognition of bacterially associated antigen. In the second aim, we will test the hypothesis that in the absence of a regulatory CD4 T cell population, effector CD4 T cells induce an antigen-specific colitis driven by bacterially associated antigen.