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

总结。T细胞通过胸腺细胞的相互作用指示T细胞对自身的耐受 与上皮细胞隔间。而胸腺是免疫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，微生物群落 肠道还调节T效应细胞的功能和外周Treg细胞(PTreg)的产生。 早期生命中粘膜组织的微生物定植促进了对共生和环境的耐受性 抗原。在此期间的不正常殖民可能会产生长期后果 在以后的生活中发展成粘膜和全身疾病。调节围产期免疫的机制- 实现长期动态平衡的系统-微生物群相互作用还没有明确的定义。我们之前 产生的小鼠(TRAF6、Δ、TEC)胸腺无髓质上皮细胞(MTECs)。MTEC 耗竭对T细胞的输出有两方面的影响：产生自身反应性T细胞和减少50% 在tTregs的数量上。TRAF6Δ受精小鼠tTregs的减少依次与：1)减少 Foxp3+Tregs和T滤泡(Tf)细胞在小肠Peyer‘s patches(PP)和 小肠炎；2)包被IgA的细菌产生扭曲；3)微生物改变 基因敲除动物肠道中的成分。综上所述，这些结果表明，异常T细胞 TRAF6-Δ-TEC小鼠胸腺产生的小室及其相关微生物区系的变化 可能会对新生的TRAF6ΔTEC小鼠的存活率产生不利影响。在本建议书中，我们将使用Traf6ΔTEC 建立小鼠模型以更好地了解T细胞和肠道微生物区系如何相互影响 围产期器官特异性耐受性。我们将检验以下假设：受损的tTreg细胞选择 TRAF6TEC小鼠，诱导其肠道微生物区系的变化，而不支持围产期耐受的诱导 以及可存活的后代。围产期基因敲除幼鼠暴露在正常微生物群中是耐受所必需的 诱导和生存。为了验证这一假设，我们将：1)检查暴露在正常微生物群中是否 足以促进新生TRAF6Δ小鼠存活并从WT中鉴定微生物群落 挽救Traf6ΔTEC新生儿存活的小鼠；2)检查是否诱导新生儿耐受 在未暴露于正常微生物区系的新生TRAF6ΔTEC小鼠中受到损害；以及3)检查 TRAF6ΔTEC小鼠T细胞亚群改变是肠道菌群失调的遗传决定因素 新生儿死亡率。定义早期生活耐受机制可能会对我们的 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性疾病。

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.