Mucosal T Cells: Is Tolerance Floating on Lipid Rafts

描述（由申请人提供）：对正常肠道免疫调节的研究描述了肠道免疫系统区别于其他外周和组织反应的基本特性。“生理性炎症”是肠道中以T淋巴细胞反应低下为特征的免疫调节状态。这种独特的，但分子未定义的性质表明主动耐受是粘膜免疫的重要组成部分。我们提出，受调节的粘膜T细胞低反应性介导肠道免疫耐受，而不受调节的T细胞激活引发炎症性肠病（IBD）。与通过CD3途径激活的外周血T细胞（PBT）形成鲜明对比的是，肠固有层T细胞（LPT）的反应是由一个使用CD2受体的替代途径主导的。我们已经开发了一种体外模型，其中LPT可以在低反应（耐受）状态和反应（保护）激活状态之间切换。使用该模型，我们证明了在两分钟内通过CD3受体复合物激活的膜近端信号在耐受性LPT中显着减少，而不是保护性LPT。我们还描述了富含胆固醇的膜微结构域，称为脂筏，不仅是质膜的结构成分，而且还定位了PBT中启动细胞内信号转导的蛋白质。凭借我们在表征LPT、分离脂质筏和描述T细胞信号转导途径方面的专业知识，我们立即准备在分子水平上研究正常粘膜中的粘膜T细胞耐受性和IBD粘膜中的异常T细胞激活。我们识别和表征LPT中脂质筏成分异质性的能力将与分子、生化和免疫学技术相结合，以验证以下中心假设：肠道T细胞的脂质筏异质性调节其信号、激活和功能，从而促进正常粘膜免疫耐受和慢性炎症。我们的目标如下：(1)评估脂质筏异质性调节耐受性LPT中TCR信号复合物正调控和负调控的结构机制。(2)通过CD2在LPT中的相互作用，研究细胞骨架与脂筏的拓扑耦合。(3)探索LPT脂筏中第二信使Ras-MAPK通路的生化调控。(4)检测IBD粘膜脂质筏调节T细胞活化的变化。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

DESCRIPTION (provided by applicant): 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 property indicates that active tolerance is an essential component of mucosal immunity. We propose that regulated mucosal T cell hypo-responsiveness mediates intestinal immune tolerance, and that unregulated T cell activation initiates inflammatory bowel disease (IBD). In striking contrast to peripheral blood T cells (PBT), which are activated via 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) state and a responsive (protective) state of activation. Using this model, we demonstrated that membrane proximal signaling within two minutes of activation through the CD3 receptor complex is markedly reduced in tolerant, but not protective LPT. We have also described that cholesterol-rich membrane micro-domains, called lipid rafts, are not only structural components of the plasma membrane, but also localize proteins for the initiation of intra-cellular signal transduction in PBT. With our expertise in characterizing LPT, isolating lipid rafts, and delineating signal transduction pathways in T cells, we are immediately poised to study mucosal T cell tolerance in the normal mucosa and aberrant T cell activation in the IBD mucosa at a molecular level. Our ability to identify and characterize heterogeneity among lipid raft constituents in LPT will be combined with molecular, biochemical, and immunological techniques to test the following central hypothesis: Lipid raft heterogeneity on intestinal T cells modulates their signaling, activation, and function, 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 regulation 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 change in the IBD T cell