Mucosal T Cells: Is Tolerance Floating on Lipid Rafts

超出提供的空间。对正常肠道免疫调节的研究已经描述了肠道免疫系统的一个基本属性，它有别于其他外周和组织反应。“生理性炎症”是肠道内的一种免疫调节状态，其特征是T淋巴细胞反应迟钝。这种独特的、但在分子上不确定的特性表明，主动耐受是粘膜免疫的一个重要组成部分。我们认为，调节性T细胞低反应性介导肠道免疫耐受，而非调节性T细胞激活I导致炎症性肠病(IBD)。与外周血T细胞(PBT)通过CD3途径激活形成鲜明对比的是，肠道固有层T细胞(LPT)的反应由另一条使用CD2受体的途径主导。我们已经建立了一个体外模型，在这个模型中，LPT可以在低反应(耐受)的S：ATE和反应(保护)的激活状态之间切换。使用这个模型，我们证明了在耐受性LPT中，通过CD3受体复合体激活2分钟内的细胞膜近端信号显著减少，但不是有效的LPT。我们还描述了富含胆固醇的膜微域，称为脂筏，不仅是质膜的结构成分，而且在PBT中也定位于启动细胞内信号转导的蛋白质。凭借我们在鉴定LPT、分离脂筏和描绘信号转导途径IJ T细胞方面的专业知识，我们立即准备在分子水平上研究正常黏膜中T细胞的耐受性和IBD粘膜中异常T细胞的激活。我们识别和表征LPT中脂筏成分的异质性的能力将与分子、生化和免疫学技术相结合来检验以下结论：中间假设：肠道T细胞上的脂筏成分的异质性调节其信号、激活和功能，从而促进正常的粘膜免疫耐受和慢性炎症。我们的目标如下：(1)评价耐受性LPT中脂筏异质性调节TCR信号复合体正负RQ调节的结构机制。(2)研究LPT中细胞骨架通过CD2与脂筏相互作用的拓扑偶联。(3)探讨LPT脂筏第二信使Ras-MAPK途径的生化调控。(4)检测脂筏对IBD黏膜T细胞活化的调节作用。我们相信，通过研究LPT信号中膜近端事件的调节以及这些事件在IBD T细胞中的变化，这种独特的方法将产生关于肠道免疫耐受和IBD的重要新信息。PERFORMANCESITE(========================================Section End===========================================

EXCEED THE SPACE PROVIDED. Investigations on the regulation of normal intestinal immunity have described a fundamental property of the intestinal immune system that distinguishes it from other peripheral and tissue responses. "Physiological inflammation" is a state of immune[ regulation in the intestine characterized by hypo-responsive T lymphocytes. This unique, but molecularly undefined _roperty indicates that active tolerance is an essential component of mucosal immunity. We propose that regulated taucosal T cell hypo-responsiveness mediates intestinal immune tolerance, and that unregulated T cell activation i fitiates inflammatory bowel disease (IBD). In striking contrast to peripherial blood T cells (PBT), which are activated vi a the CD3 pathway, intestinal lamina propria T cell (LPT) responses are dominated by an alternate pathway that uses the CD2 receptor. We have developed an in vitro model in which LPT can toggle between a hypo-responsive (tolerant) s:ate and a responsive (protective) state of activation. Using this model we demonstrated that membrane proximal signaling within 2 minutes of activation through the CD3 receptor complex is markedly reduced in tolerant, but not pro ective LPT. We have also described that cholesterol-rich membrane microdomains, called lipid rafts, are not only structtLral components of the plasma membrane, but also localize proteins for the initiation of intra-cellular signal transductio: in PBT. With our expertise in characterizing LPT, isolating lipid rafts, and delineating signal transduction pathways iJ T cells, we are immediately poised to study mucosal T cell tolerance in the normal mucosa and aberrant T cell activat on in the IBD mucosa at a molecular level. Our ability to identify and characterize heterogeneity among lipid raft ct,nstituents in LPT will be combined with molecular, biochemical, and immunological techniques to test the following _:entral hypothesis: Lipid raft heterogeneity on intestinal T cells modulates their signaling, activation, and functi)n, thereby contributing to both normal mucosal immune tolerance and chronic inflammation. Our aims are a, follows: (1) Evaluate the structural mechanisms by which lipid raft heterogeneity modulates positive and negative rq_gulation of the TCR signaling complex in tolerant LPT. (2) Investigate the topological coupling of the cytoskeleton to lipid rafts via interactions through CD2 in LPT. (3) Explore the biochemical regulation of the second messenger Ras-MAPK pathway in lipid rafts from LPT. (4) Examine changes in lipid raft modulation of T cell activation from IBD mucosa. We believe this unique approach will generate important new information on intestinal immune tolerance and IBD, by examining the regulation of membrane proximal events in LPT signaling and how these events chaqge in the IBD T cell. PERFORMANCESITE( ========================================Section End===========================================