自身免疫性胆管炎发病过程中NK细胞的免疫调节作用

Primary biliary cirrhosis (PBC) is a progressive autoimmune liver disease with cholestasis as well as destruction of intrahepatic bile ducts, which are caused by immune-mediated liver injury. Effective therapeutic methods for PBC are limited because of the difficulty in studying primary immune events during the early, asymptomatic phase of PBC and the obscure in illustrating the autoimmune mechanisms of biliary ductular damage. Our previous work found a marked increase in the frequency and absolute number of blood and liver NK cells in PBC patients. Moreover, the cytotoxic activity and perforin expression by isolated NK cells were significantly increased in PBC patients. NK cells are a critical component of the innate immune system. In addition, NK cells have significant immunoregulatory activities, as an participant in autoimmune diseases by regulating secondary immune responses. However, the role of NK cells in PBC remains unclear. This program aims to explore the mechanism of NK cells immunomodulatory effects in PBC by using PBC mouse model and NK cells-deficient PBC mouse model. The contents of this program are stated as follows: 1) Determine the role of NK cells in PBC mouse model; 2) Investigate immunological mechanisms of NK cells in the pathogenesis of PBC; 3) Explore the treatment of PBC based on the NK cells immunomodulatory effects in the progress of PBC. Through the investigation of the immunomodulatory effects of NK cells in the development of PBC, this program aims to provide theoretical foundation for the pathogenesis of autoimmune liver diseases, and also to give some guidance for clinical treatment.

原发性胆汁性肝硬化是一种由于免疫系统对自身肝脏进行攻击而引起的慢性胆汁淤积的自身免疫性肝脏疾病。由于该疾病最初免疫失衡的原因以及特异性肝脏损伤的机制仍不清楚，因此目前缺乏有效的治疗手段。我们的前期工作发现PBC患者中NK细胞出现异常。NK细胞是固有免疫的重要组成部分；同时，NK细胞也具有免疫调节功能，可以通过多种途径来影响继发性免疫，并在自身免疫性疾病中发挥作用。但NK细胞在自身免疫性肝脏疾病中所扮演的角色尚不清楚。本项目将利用PBC模型鼠和NK细胞缺失的PBC模型鼠对NK细胞在PBC中的作用机制予以探究，具体内容如下：1）确定NK细胞在PBC模型鼠发病过程中所发挥的作用；2）探究NK细胞在PBC发病过程中的分子免疫学机制；3）以NK细胞在PBC中的作用机制为基础探索PBC的治疗方法，为自身免疫性肝脏疾病的发病机理及治疗提供理论依据和临床指导。

肝脏NK细胞不同于传统的NK细胞，在维持肝脏免疫平衡方面起着重要作用。肝脏NK细胞如何参与自身免疫性胆管炎尚不清楚。利用已建立的dnTGFβRII胆管炎小鼠模型和NK细胞缺陷（Nfil3-/-）小鼠，通过过继性转输和体内抗体介导的NK细胞清除等方法，我们深入研究了NK细胞在自身免疫性胆管炎发病机制中的作用。将肝脏NK细胞的功能与其常规的NK细胞进行比较。同时进行了基因芯片分析以鉴定肝脏驻留NK细胞中的免疫抑制功能相关基因表达。我们的数据表明疾病进展与肝NK细胞比例显著降低相关。NK细胞的清除导致dnTGFβRII小鼠中的自身免疫性胆管炎加剧。我们进一步证实DX5-CD11chi肝脏NK细胞亚群与CD4+T细胞在肝内共定位并抑制了PBC小鼠模型中肝脏内CD4+T细胞增殖。基因芯片分析表明，肝脏驻留NK细胞有一个独特的基因表达模式，包括在炎症微环境中涉及负调控功能的基因表达增加等。我们的数据表明，DX5-CD11chi肝脏NK细胞通过调节CD4+T细胞增殖而显示出免疫抑制功能。因此，靶向肝脏的NK细胞可以作为PBC的组织特异性治疗策略。

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