Determinants of induced Treg and inflammatory Th17 cell balance in response to potentially pathogenic microbiota

肠道微生物区系与免疫系统细胞的相互作用控制着多种生理功能， 局部表现为肠道屏障功能的调节，全身表现为自身免疫。 疾病与抗肿瘤免疫的调节。尽管互惠互利的微生物物种通常提供了至关重要的 有益于宿主的健康，其中一些在某些情况下可能会有条件地造成损害，例如 宿主的遗传脆弱性或跟随环境扰动。这些细菌物种被称为 “病原体”被认为是炎症性肠病(IBD)的主要贡献者，如 溃疡性结肠炎和克罗恩病，以肠道生物失调为特征。一个更好的人物塑造 这些细菌的种类以及它们在健康的动态平衡中与宿主相互作用的机制 条件和期间IBD相关炎症对于开发更好的治疗方法至关重要。我们 肝螺杆菌诱导正常人调节性T细胞(ITreg)的模型研究 小鼠肠道，但当iTregs受损时，会促进Th17介导的炎症。肝片吸虫- 结肠引流的肠系膜淋巴中抗原提呈细胞(APC)激活特异性幼稚T细胞 Nodes(Mln)，并上调肠道iTreg特有的转录因子Foxp3和RORgt。 然而，当IL-10受到限制或iTreg诱导以其他方式受到影响时，微生物特异性T细胞 在固有层表达RORgt并采用致病的(P)Th17细胞程序。这项提案的目标是 是识别与MLN中单纯的H型肝炎病毒特异性T细胞相互作用的APC，以编程iTreg 或pTh17分化途径，阐明APC-T参与的分子和时间动力学 细胞相互作用，并确定不同类型的MHC II类表达细胞在肠道中的作用 固有层促进iTreg和pTh17细胞功能。在初步研究中，我们发现选择性丢失 树突状细胞(DC)中CCR7或3型固有淋巴样细胞(ILC3)中MHC-II的表达导致基因缺失 ITreg细胞分化和扩增，取而代之的是mln和固有层中的pTh17细胞。一款类似的iTreg 当参与转化生长因子-b释放的分子在DC或ILC3中发生突变时，观察到表型，提示 这种受调控的iTreg诱导细胞因子的局部释放需要幼稚的T细胞与DC和 ILC3.我们的第一个目标是通过遗传学和转录学方法精确地描述细胞类型。 在MLN中诱导iTreg所需的，并排除由于Cre在 罕见的未定性APC或细胞类型受限突变的间接影响；并确定 细胞的时空相互作用，使用多光子显微镜。第二个目标是确定《CCR7》- 在iTreg诱导受损的情况下，pTh17细胞诱导需要独立的APC(S)。第三个目标 是利用肝包虫特异的系统来研究各种不同的潜在非T细胞启动功能 肠固有层中MHC-II表达的细胞类型，包括上皮细胞和内皮细胞。

Interactions of the gut microbiota with cells of the immune system govern multiple physiological functions that are manifested locally, in the regulation of intestinal barrier functions, and systemically, in autoimmune diseases and modulation of anti-tumor immunity. Although mutualistic microbial species generally provide vital health benefits to the host, some of them can conditionally cause harm under some circumstances, such as host genetic vulnerabilities or following environmental perturbation. These bacterial species, known as “pathobionts”, have been proposed to be major contributors to inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn’s disease, which are characterized by intestinal dysbiosis. A better characterization of these bacterial species and the mechanisms by which they interact with the host in healthy homeostatic conditions and during IBD-associated inflammation is critical for developing better therapeutic approaches. We study the model pathobiont Helicobacter hepaticus, which induces regulatory T cells (iTreg) in the healthy murine gut, but promotes Th17-mediated inflammation when the iTregs are compromised. H. hepaticus- specific naïve T cells are activated by antigen-presenting cells (APCs) in colon-draining mesenteric lymph nodes (mLN), and up-regulate Foxp3 and RORgt, transcription factors characteristic of intestinal iTreg. However, when IL-10 is limiting or when iTreg induction is otherwise compromised, the microbe-specific T cells express RORgt and adopt a pathogenic (p)Th17 cell program in the lamina propria. The goals of this proposal are to identify the APCs that interact with naïve H. hepaticus-specific T cells in the mLN to program either iTreg or pTh17 differentiation pathways, elucidate the molecules involved and the temporal dynamics of the APC-T cell interactions, and determine the roles of the diverse types of MHC class II-expressing cells in the intestinal lamina propria in promoting iTreg and pTh17 cell functions. In preliminary studies, we found that selective loss of either CCR7 in dendritic cells (DCs) or MHC-II in type 3 innate lymphoid cells (ILC3) resulted in abrogation of iTreg cell differentiation and in expansion, instead, of pTh17 cells in mLN and lamina propria. A similar iTreg phenotype was observed when molecules involved in TGF-b release were mutated in DCs or ILC3, suggesting that regulated local release of this iTreg-inducing cytokine requires naïve T cells to interact with both DCs and ILC3. Our first aim is to precisely characterize, through genetic and transcriptomic approaches, the cell types required for iTreg induction in the mLN, and rule out potential for misinterpretation due to expression of Cre in rare uncharacterized APCs or to indirect effects of the cell type-restricted mutations; and determine the spatiotemporal interactions of the cells, using multiphoton microscopy. The second aim is to identify the CCR7- independent APC(s) required for pTh17 cell induction in settings of compromised iTreg induction. The third aim is to leverage the H. hepaticus-specific system to investigate potential non-T cell priming functions of diverse MHC-II-expressing cell types in the intestinal lamina propria, including epithelial and endothelial cells.