INNATE AN ADAPTIVE IMMUNITY TO MICROBIAL FLAGELLINS IN IBD

IBD中对微生物鞭毛蛋白的天然和适应性免疫。宿主免疫力丧失 对肠道微生物群的反应是实验性IBD的基础，这在人类IBD中也可能是如此。我们已经克隆并测序了一组在实验性结肠炎中作为免疫显性抗原的微生物蛋白。其中最大的一组是以前未知的厌氧肠道植物群的鞭毛蛋白，其在多种IBD小鼠模型和一半的克罗恩病患者中被免疫学识别。使用鞭毛蛋白作为探针已经揭示了在结肠炎易感的C3 H/HeJBir小鼠（C3 H）中先天免疫的明显缺陷，这是由Chr 3上的C3 H结肠炎易感基因位点（称为Cdcsl）调节的应答。巧合的是，C3 H小鼠中的这种先天性应答缺陷导致体内T细胞对鞭毛蛋白的应答增加。目的1将询问树突状细胞和巨噬细胞对微生物群的先天免疫应答是否以及如何在结肠炎易感的C3 H中与结肠炎抗性的C57 BI/6（B6）小鼠相比缺乏，以及在Cdcs 1基因座同源的C3 H和B6小鼠中缺乏。首先将细菌鞭毛蛋白和其他TLR配体用作探针，然后用从小鼠分离的革兰氏阳性和革兰氏阴性肠道细菌进行攻击。将评估C3 H与B6树突状细胞向CD 4 T细胞呈递微生物抗原的能力，以检验以下假设：对细菌的急性C3 H树突状细胞应答缺陷导致抗原向T细胞呈递，从而导致C3 H小鼠中更大的T细胞应答。我们还 将询问鞭毛蛋白是否可以通过Toll样受体5（TLR 5）作为自身或其他微生物抗原的佐剂。目的2将首次阐明IBD中对免疫显性肠道微生物抗原的适应性免疫应答是否存在明确的、重复的、非随机的传播模式。基于我们的初步数据，有待检验的假设是，在实验性IBD中确实发生了重复的、分级的表位扩散模式，与在自身免疫性疾病中观察到的相似。我们将确定这种表位扩散是否与疾病进展相关，是否需要TLR 5，是否依赖于白细胞介素-23，以及用扩散级联中早期识别的抗原免疫是否可以防止对后来识别的抗原的反应性，从而改善肠道炎症。目标3将定义T细胞在何处、何时以及如何对 使用两种新的小鼠系，干扰素γ-Thy1.1报告小鼠和对CBiM细菌鞭毛蛋白反应的TCR转基因小鼠，在结肠炎易感宿主中检测微生物抗原。这些研究将为宿主免疫系统对微生物群的反应机制以及对微生物群的异常免疫反应如何导致慢性肠道炎症提供重要的新认识。 将评估克罗恩病患者对这些抗原的先天性和适应性应答。

Innate and Adaptive Immunity to Microbial Flagellins in IBD. Abnormalities of the host immune response to the intestinal microbiota is the basis of experimental IBD, and this is likely true in human IBD as well. We have cloned and sequenced a set of microbial proteins that serve as immunodominant antigens in experimental colitis. The largest group of these were previously unknown flagellins of the anaerobic commensal flora, which were recognized immunologically in multiple mouse models of IBD and in half of patients with Crohn's disease. Use of flagellins as probes has revealed an apparent deficiency in innate immunity in colitis-prone C3H/HeJBir mice (C3H), a response regulated by a C3H colitis-susceptibility gene locus on Chr 3 termed Cdcsl. Paradoxically this deficient innate response in C3H mice results in a increased T cell response to flagellins in vivo. Aim 1 will ask whether and how the dendritic cell and macrophage innate immune response to the microbiota is deficient in colitis-prone C3H compared to colitis-resistant C57BI/6 (B6) mice, and in C3H and B6 mice that are congenic for the Cdcs1 locus. Bacterial flagellins and other TLR ligands will be used as probes first, followed by challenge with gram-positive and gram-negative intestinal bacteria isolated from mice. The ability of C3H vs B6 dendritic cells to present microbial antigens to CD4 T cells will be assessed to test the hypothesis that the deficient acute C3H dendritic cell response to bacteria prolongs antigen presentation to T cells, thus resulting in a greater T cell responses in C3H mice. Further, we will ask whether flagellins can serve as adjuvants via Toll like receptor 5 (TLR5) for themselves or for other microbial antigens. Aim 2 will address for the first time whether there is a defined, repetitive, non-random pattern of spreading of the adaptive immune response to immunodominant enteric microbial antigens in IBD. Based on our preliminary data, the hypothesis to be tested is that a repetitive, hierarchical pattern of epitope spreading does occur in experimental IBD, similar to what has been observed in autoimmune diseases. We will determine if such epitope spreading is associated with disease progression, whether it requires TLR5, whether it is dependent on lnterleukin-23, and whether immunization with antigens recognized early in the spreading cascade can prevent reactivity to antigens recognized later and thus ameliorate intestinal inflammation. Aim 3 will define where, when, and how T cells become sensitized to microbial antigens in the colitis-prone host using two novel mouse lines, an interferon gamma-Thy1.1 reporter mouse and a TCR transgenic mouse reactive to CBiM bacterial flagellin. These studies will provide important new understanding of the mechanisms by which the host immune system responds to the microbiota and how an abnormal immune response to the microbiota results in chronic intestinal inflammation. Innate and adaptive response of Crohn's patients to these antigens will be assessed.