Mechanisms of immune homeostasis and regulation of intraocular inflammation

一些器官特异性自身免疫性疾病，如葡萄膜炎和多发性硬化症，是由自身反应性CD4+T细胞介导的，其特点是爆炸性炎症发作的不可预测的重复周期，可以自发消退(无需治疗)。发作之间，眼睛或大脑几乎没有炎症的迹象。在这项研究中，我们建立了一种慢性葡萄膜炎的长期小鼠模型，并使用该模型来解决一个古老的问题，即在炎症缓解期间，介导反复缓解周期和复发性自身免疫性疾病的自身反应性记忆T细胞驻留在哪里。我们用IRBP/CFA免疫小鼠建立了实验性自身免疫病(EAU)模型，并通过眼底镜、组织病理学、光学相干断层扫描(OCT)和视网膜电成像(ERG)对疾病的进展进行了6个月的监测。以Th1/Th17细胞大量渗入视网膜为特征的EAU高峰期在发病后第21天出现，但在免疫后第30天病情开始缓解，血液或视网膜中检测到的细胞很少。我们利用非常敏感的抗原诱导的CD154表达分析来追踪自身反应性T细胞的位置，这些T细胞在免疫后30到225天持续存在于周围组织中。我们发现，急性葡萄膜炎发病几个月后，残留的视网膜自身抗原自身反应性T细胞IRBP重新定位到骨髓(BM)。IRBP特异性记忆T细胞(IL-7R#945；HiLy6CHiCD4+)在静息状态下驻留在骨髓中，但在再次刺激后转化为IL-17/干扰素表达的效应细胞(IL-7R#945；LowLy6CLowCD4+)。我们进一步表明，在骨髓中募集和保留IRBP特异性记忆T细胞需要通过STAT3依赖的机制诱导骨桥蛋白的表达。我们使用WT慢性葡萄膜炎小鼠的BM细胞过继地将葡萄膜炎转移到NAVE小鼠，但不使用IRBP免疫的STAT3缺陷(CD4-STAT3KO)小鼠的BM细胞。确认BM是导致葡萄膜炎的T细胞的生存利基，表明BM基质细胞为自身反应性记忆T细胞提供生存信号，以及STAT3依赖的机制介导它们重新定位到BM，是有吸引力的治疗靶点，可以被用来选择性地耗尽驱动慢性炎症的记忆T细胞。

Several organ-specific autoimmune diseases such as uveitis and multiple sclerosis are mediated by autoreactive CD4+ T cells and are characterized by unpredictable repetitive cycles of explosive inflammatory attacks, which can subside spontaneously (without treatment). Between attacks, there can be little or no evidence of inflammation in the eyes or brain. In this study, we established a long-term mouse model of chronic uveitis and used this model to address the age-old question of where the autoreactive memory T cells that mediate the repeated cycles of remission and recurrent autoimmune disease reside during remissions of inflammation. We induced experimental autoimmune disease (EAU) in mice by immunization with IRBP/CFA and monitored progression of the disease over a period of 6 months by funduscopy, histophathology, optical coherence tomography (OCT) and eletroretinography (ERG). Peak EAU characterized by massive infiltration of Th1/Th17 cells in retina was observed 21 days after disease induction but by day-30 post-immunization the disease went into remission with very few cells detectable in blood or retina. We utilized the very sensitive antigen-induced CD154 expression assay to trace the location of autoreactive T-cells that persist in peripheral tissues over time, starting 30 to 225 days post-immunization. We show that several months after inception of acute uveitis that residual autoreactive memory T-cells specific to retinal autoantigen, IRBP, relocated to bone marrow (BM). The IRBP-specific memory T-cells (IL-7RαHiLy6CHiCD4+) resided in BM in resting state but upon re-stimulation converted to IL-17-/IFN-γ-expressing effectors (IL-7RαLowLy6CLowCD4+). We further show that recruitment into and retention of IRBP-specific memory T-cells in BM required induction of α4β1 and osteopontin expression by STAT3-dependent mechanism. We adoptively transferred uveitis to nave mice using BM cells from WT mice with chronic uveitis but not with BM cells from IRBP-immunized STAT3-deficient (CD4-STAT3KO) mice. Identifying BM as survival-niche for T-cells that cause uveitis, suggests that BM stromal cells that provide survival signals to autoreactive memory T-cells and STAT3-dependent mechanisms that mediate their relocation into BM, are attractive therapeutic targets that can be exploited to selectively deplete memory T-cells that drive chronic inflammation.