Microbiota-mediated T cell tolerance in newborn and adult autoimmunity-prone mice

摘要通过胸腺细胞的相互作用，T细胞对自身耐受的指令发生在胸腺中 与上皮细胞区室的关系。胸腺是免疫T细胞的主要部位， 对自身抗原的耐受性和胸腺T调节细胞（tTreg）的产生， 肠还调节T效应细胞（Teff）的功能和外周Treg细胞（pTreg）的产生。 生命早期粘膜组织的微生物定殖促进对唾液和环境的耐受性 抗原在此期间的异常殖民化可能会产生长期后果， 在以后的生活中发生粘膜和全身性疾病。调节围产期免疫的机制- 实现长期体内平衡的系统-微生物群相互作用的定义很差。我们之前 产生胸腺缺乏胸腺髓质上皮细胞（mTECs）的小鼠（Traf 6 ΔTEC）。MTEC 耗尽对T细胞输出有两方面的影响：自身反应性T细胞的产生和减少50% 的数量。Traf 6 ΔTEC小鼠中tTdR的降低反过来与以下相关：1）降低 小肠派伊尔集合淋巴结（PP）中Foxp 3 + T淋巴细胞和T滤泡（Tf）细胞的数量， 小肠炎症; 2）IgA包被细菌的偏斜产生;和3）改变的微生物 基因敲除动物肠道中的组成。总之，这些结果表明，异常的T细胞 Traf 6 ΔTEC小鼠胸腺中产生的隔室和微生物群的相关变化 可能对新生Traf 6 ΔTEC小鼠的存活率产生不利影响。在本提案中，我们将使用Traf 6 ΔTEC 小鼠模型，以更好地了解T细胞和肠道微生物群如何相互影响， 围产期器官特异性耐受。我们将检验以下假设： Traf 6 ΔTEC小鼠诱导其肠道微生物群的变化，但不能支持诱导围产期耐受 和有活力的后代基因敲除幼崽围产期暴露于正常微生物群是耐受所必需的 诱导和生存。为了验证这一假设，我们将：1）检查暴露于正常微生物群是否 足以促进新生Traf 6 ΔTEC小鼠的存活并识别WT中的微生物群落 拯救Traf 6 ΔTEC新生儿存活的小鼠; 2）检查新生儿耐受的诱导是否 在未暴露于正常微生物群的新生Traf 6 ΔTEC小鼠中受损;以及3）检查 Traf 6 ΔTEC小鼠T细胞区室的改变是肠道生态失调的遗传决定因素， 新生儿致死率定义生命早期的耐受机制可能会对我们的生活产生深远的影响。 了解人类自身免疫性疾病的发展，并可能帮助我们设计新的策略， 管理和/或治疗T细胞介导的自身免疫疾病。

SUMMARY. Instruction of T cells to be tolerant to self occurs in the thymus through interactions of thymocytes with the epithelial cell compartment. While the thymus serves as the primary site of immunologic T cell tolerance to self-antigens and production of thymic T regulatory (tTreg) cells, microbial communities in the gut also regulate the function of T effector (Teff) cells and production of peripheral Treg cells (pTreg). Microbial colonization of mucosal tissues in early life facilitates tolerance to commensal and environmental antigens. Abnormal colonization during this period can have long-term consequences contributing to development of mucosal and systemic disease later in life. The mechanisms that regulate perinatal immune- system-microbiota interactions to achieve long-term homeostasis are poorly defined. We previously generated mice (Traf6ΔTEC) whose thymus was devoid of medullary thymic epithelial cell (mTECs). mTEC depletion had a two-faceted effect on the T cell output: generation of autoreactive T cells and a 50% reduction in the numbers of tTregs. The reduction in tTregs in Traf6ΔTEC mice in turn associated with: 1) reduced numbers of Foxp3+ Tregs and T follicular (Tf) cells in the Peyer’s Patches (PP) of the small intestine and small intestinal inflammation; 2) skewed production of IgA-coated bacteria; and 3) altered microbial composition in the gut of knockout animals. Together, these results suggest that the aberrant T cell compartment generated in the thymus of Traf6ΔTEC mice and associated changes in the microbiota may adversely impact survival of newborn Traf6ΔTEC mice. In this proposal we will use the Traf6ΔTEC mouse model to better understand how T cells and the gut microbiota influence each other to establish perinatal organ-specific tolerance. We will test the following hypothesis: Impaired tTreg cell selection in Traf6ΔTEC mice, induces changes in their gut microbiota that cannot support induction of perinatal tolerance and viable progeny. Perinatal exposure of knockout pups to normal microbiota is required for tolerance induction and survival. To test this hypothesis we will: 1) examine whether exposure to normal microbiota is sufficient for promoting survival of newborn Traf6ΔTEC mice and identify microbial communities from WT mice that rescue Traf6ΔTEC neonate survival; 2) examine whether induction of neonatal tolerance is compromised in newborn Traf6ΔTEC mice that are not exposed to normal microbiota; and 3) examine if the altered T cell compartment of Traf6ΔTEC mice acts as a genetic determinant of intestinal dysbiosis and neonatal lethality. Defining early-life tolerance mechanisms could have a profound impact on our understanding of human autoimmune disease development and may help us devise novel strategies for managing and/or treating T cell mediated autoimmune diseases.