Role of Dendritic Cells in H pylori-induced Treg-mediated Host Immune Tolerance

描述（由申请人提供）：黏膜对肠道微生物的免疫耐受是一个高度调控的过程，缺乏免疫耐受可导致胃肠道慢性炎症。幽门螺杆菌是一种胃病原体，能在<15%的感染者中引起严重的慢性胃炎和溃疡，但大多数人发展为无症状的轻度胃炎。这项建议的长期目标是了解胃粘膜耐受的机制。我们将在K08资助期间的观察基础上，研究树突状细胞（DCs）介导的幽门螺杆菌免疫逃逸机制，并使用幽门螺杆菌定植模型研究胃粘膜耐受。我们的初步结果支持Hp诱导调节性T细胞（Tregs）是由dc介导的这一观点。因此，我们假设幽门螺杆菌通过irak -m介导的tgf -2依赖机制与dc相互作用，从而触发宿主的耐受性反应，改变幽门螺杆菌Teffector/Treg平衡，导致宿主对幽门螺杆菌的耐受性和慢性定植。具体目的是：目的1)确定组织dc在幽门螺杆菌耐受中的作用。急性幽门螺杆菌感染期间胃内DC亚群的特征，以及DC对幽门螺杆菌摄取和淋巴结迁移的机制将被阐明。DC在幽门螺杆菌摄取和耐受性诱导中的需求将通过DC消融来研究。目的2)研究DC TLR和细胞内调节剂在耐受性DC编程中的作用。首先，我们将确定幽门螺杆菌刺激dc诱导Tregs是否需要免疫原性幽门螺杆菌。接下来，我们将探讨IRAK-M在Treg诱导中的作用。TLR9的作用也将通过幽门螺杆菌DNA刺激和TLR9缺失小鼠进行探讨。目的3)分析DC-Treg诱导在调节幽门螺杆菌耐受中的作用。我们将在小鼠体内过继转移幽门螺杆菌刺激的bmdc，诱导幽门螺杆菌特异性Treg，然后使用CD25中和抗体研究Treg消耗对幽门螺杆菌耐受的影响。Th1和Th17细胞在幽门螺杆菌耐受中的作用将在IFN-3和Th17A缺失的小鼠中进行研究。调节TGF-2对幽门螺杆菌刺激的dc诱导Treg的影响将通过使用过表达TGF-2或产生TGF-2受体在微环境中中和dc的细胞系进行研究。本建议的健康相关性在于了解粘膜对幽门螺杆菌的耐受机制，从而开始解决导致耐受降低的因素。本项目的发现不仅将为肠道细菌的粘膜耐受机制提供新的见解，而且还将增强我们对胃免疫室耐受发展的理解。通过靶向dc调节机制或使用细菌产物（如益生元、益生菌），可能会发现新的靶点，有助于设计治疗方法，以恢复慢性炎症患者的免疫稳态。

DESCRIPTION (provided by applicant): Mucosal immune tolerance to luminal microbes is a highly regulated process a lack of which leads to chronic inflammation of the GI tract. H. pylori is a gastric pathogen able to cause severe chronic gastritis and ulcers in <15% of infected individuals, but the majority developed a mild gastritis without symptoms. The long-term objective of this proposal is to understand the mechanisms of mucosal tolerance in the stomach. We will build on our observations made during the K08 funding period studying the dendritic cells (DCs)-mediated mechanism of H. pylori immune escape and use the H. pylori colonization model to study gastric mucosal tolerance. Our preliminary results support the notion that Hp induction of regulatory T cells (Tregs) is mediated by DCs. Therefore, we hypothesize that H. pylori triggers a host tolerogenic response by interacting with DCs via a IRAK-M-mediated, TGF-2-dependent mechanism which alters the H. pylori Teffector/Treg balance leading to the development of host tolerance to H. pylori and chronic colonization. The specific aims are: Aim 1) To Determine the role of tissue DCs in H. pylori tolerance. DC subset in the stomach will be characterized during acute H. pylori infection and mechanism of H. pylori uptake and lymph node migration by DC will be elucidated. The requirement of DCs in H. pylori uptake and tolerance induction will be studied using DC ablation. Aim 2) Investigate the role of DC TLR and intracellular modulators of tolerogenic DC programming. First we will determine whether H. pylori stimulated DCs induce Tregs requires immunogenic H. pylori. Next, the role of IRAK-M in Treg induction will be explored. The role of TLR9 will also be explored using H. pylori DNA stimulation and TLR9 null mice. Aim 3) To analyze the role of DC-Treg induction in modulating H. pylori tolerance. We will use in vivo adoptive transfer of H. pylori-stimulated BMDCs into mice to induce H. pylori- specific Tregs and then use CD25 neutralizing antibodies to study the effect of Treg depletion on H. pylori tolerance. The role of Th1 and Th17 cells in H. pylori tolerance will be studied using IFN-3 and Th17A null mice. The effect of modulation TGF-2 on Treg induction by H. pylori stimulated DCs will be studies using cell lines over-expressing TGF-2 or produces a TGF-2 receptor that neutralizes DCs in the microenvironment. The health relatedness of this proposal is to understand the mechanism of mucosal tolerance to H. pylori to begin to address the factors that lead to reduced tolerance. The finding of this project will provide not only provide novel insight into the mechanism of mucosal tolerance to luminal bacteria, but also enhance our understanding of the development of tolerance in the gastric immune compartment. New targets may be discovered useful for designing therapies to restored immune homeostasis in patients with chronic inflammatory conditions by targeting DCs regulatory mechanisms or by using bacterial products (e.g., prebiotics, probiotics). PUBLIC HEALTH RELEVANCE: The health relatedness of this proposal is to understand the mechanism of mucosal tolerance in order to begin to address the factors that lead to a break in tolerance. The finding of this project will provide not only provide novel insight into the mechanism of mucosal tolerance to luminal bacteria, but also enhance our understanding of the development of tolerance in the gastric immune compartment. New targets may be discovered useful for designing therapies to restored immune homeostasis in patients with chronic inflammatory conditions by targeting DCs regulatory mechanisms or by using bacterial products (e.g., prebiotics, probiotics).