Gut microbiome influences on autoimmune disease

描述（由申请人提供）：人类物种与一系列肠道微生物共同进化了数十万年，这种共生关系现在因生活方式、卫生或广泛使用抗生素的深刻变化而改变，这些变化可能与过敏或自身免疫性疾病的发病率增加有关。肠道微生物强烈影响免疫细胞分化，如分段丝状细菌（SFB）所例示，其是一种肠道驻留厌氧菌，其促进产生IL 17的“Th 17”细胞的分化，这进而释放Th 17依赖性自身免疫疾病。该项目将分析SFB> Th 17轴的机制，这是微生物对免疫功能影响的一个定义明确且易于处理的模型系统。SFB在小肠中诱导的变化的基因表达谱分析提出了几个有趣的候选人，我们已经获得了正式的证据，其中之一，血清淀粉样蛋白SAA 3，构成了级联反应中的重要中继。我们将在这些结果的基础上分析SFB和Th 17分化之间的相互作用，以及SFB的影响如何受到其他微生物或环境影响的影响和整合。1.鉴定SFB在体内诱导Th 17分化的细胞和分子序列。我们推测，SFB在与其相互作用的上皮细胞中启动了一个级联反应，通过树突状细胞的巨噬细胞传递，最终促进了CD 4 + αβT细胞的Th 17分化。基因组分析表明，SFB诱导许多基因的表达，这些基因的产物可能在级联反应中起中间体的作用：血清淀粉样蛋白SAA 3（我们已经开始确定其重要性）和其他候选基因（SAA 1、iNOS、抵抗素-β）。我们将绘制事件顺序：（i）鉴定诱导这些推定中间体的细胞类型;（ii）用诱导型转基因和敲除小鼠评估反应的哪个部分映射到每个中间体的下游。2. SAA 3如何诱导αβT细胞中的Th 17重组SAA 3可以诱导Th 17分化，但仅在髓系CD 11b + od CD 11 c+细胞存在下。我们将通过确定哪些髓样细胞可以作为必需的辅因子，分析SAA 3触发的信号通路，并测试可能诱导和需要的中间细胞因子来建立起作用的机制。3. SFB效应是否受到其他微生物或环境辅助因子的调节？SFB的影响可能受到其他肠道物质或饮食因素的调节。我们将通过将SFB效应中的微观异质性与由微生物群落遗传谱确定的其他细菌家族的丰度相关联，以及通过测试SFB诱导的Th 17细胞和关节炎表现如何受到饮食元素（Ahr配体，NaCl）的影响来测试这一概念。这些研究应该为肠道微生物群如何改变宿主的免疫系统和调节自身免疫性疾病的风险提供新的机制见解，这些机制信息可能为解决人类自身免疫性疾病提出新的策略。

DESCRIPTION (provided by applicant): The human species has co-evolved over hundreds of millennia with an array of commensal microbes, a symbiotic relationship now altered by profound changes in lifestyle, hygiene, or widespread antibiotic use, changes that may be linked to the increasing incidence of allergy or autoimmune diseases. Intestinal microbes strongly influence immune cell differentiation, as exemplified by Segmented Filamentous Bacteria (SFB), a gut- resident anaerobe which promotes the differentiation of IL17-producing "Th17" cells, which in turn unleash Th17-dependent autoimmune diseases. This project will analyze the mechanisms of the SFB>Th17 axis, a well-defined and tractable model system of the microbial influence on immune function. Gene expression profiling of changes induced by SFB in the small intestine brought forth several intriguing candidates, and we have obtained formal evidence that one of them, the serum amyloid protein SAA3, constitutes an essential relay in the cascade. We will build on these results to analyze the interplay between SFB and Th17 differentiation, and how the effects of SFB are influenced and integrated within other microbial or environmental influences. 1. Identify the sequence of cells and molecules through which SFB induces Th17 differentiation in vivo. We hypothesize that SFB elicits a response cascade, initiated in the epithelial cells with which SFB interacts, transmitted via macrophages of dendriti cells, which ultimately promotes the Th17 differentiation of CD4+ αβT cells. Genomic profiling show that SFB induces the expression of a number of genes whose products may function as intermediates in the cascade: the serum amyloid SAA3 whose importance we have begun to establish, and other candidates (SAA1, iNOS, Resistin-β). We will chart the sequence of events: (i) identify the cell-types in which these putative intermediates are induced; (ii) assess with inducible transgenesis and knockout mice which segment of the response maps downstream of each intermediate. 2. How SAA3 induces the Th17 in αβT cells. Recombinant SAA3 can induce Th17 differentiation but only in the presence of myeloid CD11b+ od CD11c+ cells. We will establish the mechanism at play by establishing which myeloid cell(s) can serve as the essential cofactor, analyzing which signaling pathways are triggered by SAA3, and testing which intermediate cytokines may be induced and required. 3. Are SFB effects modulated by, other microbes or environmental cofactors. It is likely that SFB's influence is modulated by other gut commensals, or by dietary factors. We will test this notion by correlating the micro- heterogeneity in SFB's effects with the abundance of other bacterial families, determined by microbial community genetic profiling, and by testing how SFB-induced Th17 cells and arthritis manifestations are influenced by dietary elements (Ahr ligands, NaCl). These studies should provide novel mechanistic insights into how the gut microbiota alters the host's immune system and modulate the risk of autoimmune diseases, mechanistic information which may suggest new strategies for addressing human autoimmune disease.