骨桥蛋白对TLR3介导的胸腺免疫微环境变化及AchR抗体产生的影响及作用机制

Imbalance of innate immunity caused by virus infection may be an important initiating step in inducing myasthenia gravis (MG), and the induced changes in thymic microenvironment are very important in the pathogenesis of MG. Studies have shown that TLR3 activator poly (I: C) induces the expression of AchR in thymic epithelial cells, recruits B cells and induces AchR-specific antibody production. Whether innate immune cells such as dendritic cells and macrophages in the thymus are involved in this process still remains unclear. Osteopontin (OPN) is an immunomodulatory factor of great interest in recent years. Our previous study showed that poly (I: C) increased expression of OPN in thymus epithelial cells. The present study is aimed to explore the characteristics of the immunological microenvironment of thymus in MG patients, especially the changes of dendritic cells and macrophages. Furthemore, the effect of poly (I: C) on dendritic cells and macrophages, as well as the role of OPN will be explored within in vitro cellular experiment. In addition, in vivo experiments will be utilized to explore the impact of blocking OPN on the thymic microenvironment and anti-AchR antibody production. This study focuses on poly (I: C) -induced changes of thymic microenvironment, evaluates the effect of OPN induced by TLR3 activation on thymic macrophages and dendritic cells, and explores underlying mechanisms.

病毒感染引起的固有免疫失衡可能是诱发重症肌无力（MG）的重要始动环节，由此诱发的胸腺免疫微环境变化在MG的发病过程中至关重要。研究证实TLR3激活剂poly（I:C）可诱导胸腺上皮细胞表达AchR，募集B细胞，诱导AchR特异性抗体产生，而胸腺中固有免疫细胞，如树突状细胞、巨噬细胞是否参与此过程尚不清楚。骨桥蛋白（OPN）是近年备受关注的免疫调节因子，我们在前期研究中发现poly（I:C）可诱导胸腺上皮细胞OPN表达增加。本课题拟通过临床标本探索MG胸腺免疫微环境的特征，尤其是树突状细胞、巨噬细胞的变化；通过细胞实验明确poly（I:C）对树突状细胞、巨噬细胞的影响，以及OPN的作用；通过动物实验探索阻断OPN对胸腺免疫微环境及AchR抗体产生的影响。本课题聚焦于poly（I:C）诱导的胸腺免疫微环境变化，重点研究TLR3活化诱导上调的OPN对胸腺巨噬细胞、树突状细胞的影响，并探索其机制。

病毒感染可影响机体免疫功能，本研究中我们证实病毒类似物poly（I:C）可通过改变胸腺微环境加重小鼠重症肌无力症状，表现为胸腺内CD80+细胞增多，IFN-γ+和IL-10+细胞增多，CD4+Foxp3+细胞减少，其机制可能是由骨桥蛋白介导的。给予抗骨桥蛋白抗体则明显减轻poly（I:C）导致的症状加重，其机制可能与改善了胸腺微环境有关。另外，本研究还发现poly（I:C）注射后胸腺发生一过性萎缩，模拟病毒胁迫下胸腺发生的生理学变化。通过比较小鼠胸腺在胁迫状态及恢复期的转录组谱，我们发现多条免疫调节通路参与胸腺对病毒的响应，并且在恢复期胸腺仍处于对病毒应答的响应状态，提示胸腺可能存在胁迫记忆，即在遭受二次胁迫后可迅速应答，提高对病毒胁迫的耐受性，有利于机体迅速恢复正常的免疫功能。