Local immune tolerance in the large intestine mediated by GPR15

项目摘要/摘要 至关重要的是，宿主免疫系统不会对外来病毒产生直接的炎症反应。 肠腔中丰富的抗原(如通过小肠暴露的饮食抗原 粘膜和微生物抗原主要来自大肠的管腔)。在这方面的失败 这一过程对宿主的健康造成了严重威胁，这一点从乳糜泻的流行和 炎症性肠病。调节性T细胞(Tregs)已经进化为在确保这一点上发挥关键作用 宽容。已知饮食抗原可产生可诱导的树突状细胞(ITregs)和系统对 这些抗原是通过这些iTregs在体内循环实现的(口服耐受)。相比之下，它 可能不利于宿主建立系统的、Treg介导的对来自 由于大肠自复制微生物是大肠抗原的主要来源，所以很容易 逃逸并侵入肠道外的组织。我们的长期目标是描述Treg如何通过 对来自大肠的抗原的耐受性已经实现。我们的中心假设是激活 T细胞芳香烃受体(AHR)诱导GPR15表达并促进iTreg分化 同时产生GPR15+iTregs，GPR15-C10orf99受体-配体对介导 Tregs在大肠中的滞留，防止iTregs的全身扩散，实现局部 GPR15+iTregs的耐受性。在强大的初步数据的指导下，我们已经产生了新的老鼠模型 将使我们能够检验这些假说。我们建议追求以下两个目标：(1)表征 大肠和全身口服Treg介导的对微生物抗原免疫耐受的比较 对来自小肠的饮食抗原的耐受性，我们将检查GPR15-C10orf99是否介导 Tregs在大肠固有层内的运输和Treg滞留 在渗出过程中起作用。我们还将决定GPR15+iTregs的命运和在 GPR15可诱导缺失后Treg介导的对肠道微生物抗原的耐受。(2)刻画 AHR信号在iTreg分化和GPR15诱导中的作用，我们将用已报道的化学物质进行测试 AHR配体活性为其诱导FOXP3和GPR15表达的能力。我们还将检查 AHR诱导体内GPR15+Tregs增加的细胞水平机制。要了解 AHR介导FOXP3和GPR15表达的分子机制，我们将进行CHIPseq 分析AHR激活后的T细胞中的特定配体，我们将对其进行鉴定。我们的发现将显著地 加深对Treg介导的耐受的理解，将有助于开发新的治疗策略 治疗各种免疫性疾病。

PROJECT SUMMARY/ABSTRACT It is critical that the host immune system does not mount outright inflammatory responses against foreign antigens abundant in the lumen of the intestine (such as dietary antigens exposed through the small intestine mucosa and microbial antigens coming predominantly from the lumen of the large intestine). Failure in this process leads to a significant health threat to the host as evidenced by prevalence of celiac disease and inflammatory bowel diseases. Regulatory T cells (Tregs) have evolved to play a critical role to ensure this tolerance. Dietary antigens are known to generate inducible Tregs (iTregs) and systemic tolerance against those antigens is achieved by circulation of these iTregs throughout the body (oral tolerance). In contrast, it may not be beneficial for the host to establish systemic, Treg-mediated tolerance against antigens from the large intestine since self-replicating microbes, the primary source of antigens in the large intestine, can easily escape and invade tissues outside of the intestine. Our long-term goal is to characterize how Treg-mediated tolerance against antigens from the large intestine is accomplished. Our central hypotheses are that activation of the aryl hydrocarbon receptor (AHR) in T cells induces GPR15 expression and promotes iTreg differentiation simultaneously to produce GPR15+ iTregs and that the GPR15-C10orf99 receptor-ligand pair mediates the retention of Tregs in the large intestine and prevents systemic dissemination of iTregs, accomplishing local tolerance by GPR15+ iTregs. Guided by strong preliminary data, we have generated novel mouse models that will enable us to test these hypotheses. We propose to pursue the following two aims: (1) To characterize Treg-mediated immune tolerance against microbial antigens in the large intestine compared to systemic oral tolerance against dietary antigens from the small intestine, we will check whether GPR15-C10orf99 mediate trafficking of Tregs inside the large intestine lamina propria and Treg retention, in addition to their known function during extravasation. We will also determine the fate of GPR15+ iTregs and the consequences in Treg-mediated tolerance against gut microbial antigens after inducible deletion of GPR15. (2) To characterize the effect of AHR signaling on iTreg differentiation and GPR15 induction, we will test chemicals with reported AHR ligand activity for their ability to induce FOXP3 and GPR15 expression. We will also examine mechanisms underlying AHR-induced increase of GPR15+ Tregs in vivo at the cellular level. To understand the molecular mechanisms for AHR-mediated expression of FOXP3 and GPR15, we will perform CHIPseq analysis in T cells after AHR activation by specific ligands that we will identify. Our findings will significantly advance understanding of Treg-mediated tolerance and will help to develop novel therapeutic strategies to treat various immunological disorders.