T cell Tolerance to Enteric Commensal Bacteria

项目摘要 胃肠道是由大量的肠道细菌生活在 与主人和谐相处。这对免疫系统提出了挑战，免疫系统必须促进对 有益的细菌种类，同时仍然提供针对致病性种类的保护。事实上， 这种歧视被认为是炎症性肠病（IBD）的主要潜在原因。 与自身抗原不同，来源于肠道微生物群的抗原不太可能存在于细胞内。 胸腺影响中枢T细胞耐受性。相反，对这些抗原的特异性耐受必须完全依赖于 在肠道的免疫环境内起作用的外周机制。然而，这些机制和 它们介导的耐受性的质量尚不清楚。为了更好地研究这些过程，我们的实验室 开发的肽：MHCII四聚体试剂，使我们能够直接识别罕见的肠道CD 4 + T细胞， 对小鼠中来自几种不同肠道细菌物种的免疫显性表位的特异性。我们 初步研究支持缺失、Treg和Tr 1细胞发育的不同作用，这取决于细菌 物种为了提供更好的免疫抗原特异性T细胞表型的分辨率以及免疫原性， 由于这些表型在整个抗原特异性群体中的异质性，我们将结合使用 四聚体与单细胞RNA-seq转录组学，以全面定义表型和克隆 在不同的淋巴细胞抗原特异性CD 4 + T细胞群体内的异质性。 该项目的首要目标是了解T细胞维持免疫的机制。 对胃肠道特定细菌的耐受性，使它们最终可以 为了治疗效果而操纵。我们假设对大肠杆菌抗原的耐受性是 由多种CD 4 + T细胞命运维持，每种都做出独特但重叠的功能贡献， 面对动态的肠道环境，共同建立持久的耐受性。我们将检验这一假设 通过1）定义有助于以下的肠道细菌抗原特异性CD 4 + T细胞的发育命运： 免疫耐受，和2）表征免疫抗原特异性调节性T细胞亚群的功能。

PROJECT SUMMARY The gastrointestinal tract is colonized by an enormous collection of commensal bacteria living in harmony with the host. This poses a challenge for the immune system which must promote tolerance to beneficial bacteria species while still providing protection against pathogenic species. Indeed, a breakdown in such discrimination is thought to be a major underlying cause of inflammatory bowel disease (IBD). Unlike self-antigens, antigens derived from commensal microbiota are unlikely to be presented in the thymus to impact central T cell tolerance. Rather, specific tolerance to these antigens must rely exclusively on peripheral mechanisms acting within the immune environment of the gut. However, these mechanisms and the quality of the tolerance they mediate are unclear. To better investigate these processes, our lab has developed peptide:MHCII tetramer reagents that enable us to directly identify rare gut CD4+ T cells with specificity to immunodominant epitopes from several different commensal bacteria species in mice. Our preliminary studies support varied roles for deletion, Treg, and Tr1 cell development depending on the bacteria species. To provide better resolution of commensal antigen-specific T cell phenotypes as well as the heterogeneity of these phenotypes within the overall antigen-specific population, we are combining our use of tetramers with single cell RNA-seq transcriptomics to comprehensively define phenotypic and clonal heterogeneity within distinct commensal antigen-specific CD4+ T cell populations. The overarching goal of this project is to understand the mechanisms by which T cells maintain immune tolerance to specific commensal bacteria of the gastrointestinal tract so that they may ultimately be manipulated for therapeutic benefit. We hypothesize that tolerance to commensal bacterial antigens is maintained by multiple CD4+ T cell fates, each making unique but overlapping functional contributions that collectively establish durable tolerance in the face of the dynamic gut environment. We will test this hypothesis by 1) defining developmental fates for commensal bacterial antigen-specific CD4+ T cells that contribute to immune tolerance, and 2) characterizing the function of commensal antigen-specific regulatory T cell subsets.