埃兹蛋白（Ezrin）磷酸化介导的穿入现象在自身免疫性肝炎发病中的作用和机制

Autoimmune hepatitis (AIH) is an abnormal autoimmune reaction mediates inflammatory lesions of the liver parenchyma, may progress to cirrhosis.Although emeripolesis (cell in cell phenomena) is regarded as one of the characteristic features in AIH, the cell types, end and mechanisms have not been studied. Our early experiments in liver tissues confirmed that CD8 T cells were the major immune cells inside hepatocytes, phosphorylation of ezrin/radixin/moesin(p-ERM) was highly expressed in contact between CD8 T cells and hepatocytes, apoptosis was induced in both of them after emperipolesis. It has been confirmed phosphorylation of threonine 567 in Ezrin protein(Ezrin pThr567) plays important role in cell polarity change and migration. We assume that under normal circumstances, auto-reactive CD8 T cells which expression of Ezrin(pThr567)infiltrate into liver cells undergo apoptosis in order to maintain its steady-state. An excess of CD8 T cells can cause liver cell damage, leading to incidence of AIH. Our research focus on emperipolesis in the pathogenesis of AIH and intend to answer the following questions:1)the consequence of CD8 T cell and hepatocyte after emperipolesis; 2)the mechanism of emperipolesis. Through research,We will provide new discoveries on pathogenesis of AIH and thus provide new ways for its prevention.

自身免疫性肝炎(AIH)是由异常的自身免疫反应介导的肝实质炎症性病变，可进展至肝硬化。虽然穿入现象已作为AIH的特征性组织学表现，但穿入细胞的类型、结局、机制尚未系统研究。我们前期实验在肝组织上证实CD8 T细胞是发生穿入的主要细胞，其穿入后可诱发肝细胞及自身凋亡，穿入时两细胞接触处高表达磷酸化的埃兹蛋白/根蛋白/膜突蛋白复合体(p-ERM), 而埃兹蛋白567位苏氨酸磷酸化（Ezrin pThr567)在细胞极性改变和迁移中的作用已被证实。我们假设：正常情况下，自身反应的CD8 T细胞表面高表达Ezrin(pThr567)穿入肝细胞内诱发自身凋亡，维持机体稳态。当这类CD8 T细胞过量时会引起肝细胞损伤，导致AIH的发生。本研究以AIH中穿入现象为切入点，拟回答以下科学问题：1）穿入后两种细胞的结局；2）穿入发生的机制。通过研究，尝试就AIH的发病机制提供新发现进而为其防治提供新途径。

穿入现象是自身免疫性肝炎（AIH）组织学特征之一。前期我们研究在人肝脏组织学上已证实CD8阳性T细胞参与穿入，本研究我们通过体外实验和小鼠造模(α-GalCer)来研究穿入的机制。我们采集不同肝脏疾病患者和健康对照者外周血单个核细胞(PBMC)与人肝细胞系共培养。共聚焦荧光染色明确体外穿入细胞类型和可能的机制。此外运用α-GalCer造模小鼠模拟AIH来证实CD44/p-ERM/F-actin在穿入中的作用。研究发现：在体外PBMC和人肝细胞系培养体系中，AIH组较其他肝病组及正常对照组发生穿入的比例更高。CD8阳性T细胞是发生穿入的主要细胞，其通过CD44/p-ERM/F-actin途径进入肝细胞，最终大部分自身凋亡。在α-GalCer诱导的肝炎小鼠模型中，穿入现象可被ezrin磷酸化抑制剂NSC668394抑制，活化的小鼠CD8阳性T细胞同样通过CD44/p-ERM/F-actin途径穿入小鼠原代肝细胞。由此我们得出结论： CD8阳性T 细胞通过CD44/p-ERM/F-actin途径穿入肝细胞并发生凋亡，这可能是机体保护机制，但在异常免疫情况下过量的CD8 T细胞穿入肝细胞会损伤肝脏导致AIH的发生。本研究为AIH的发病机制及诊治提供新思路。