小鼠肝脏特有NK细胞的免疫负调功能及其与肝脏免疫耐受特性的维持

NK cells are heterogeneity population and currently explored for their killing effects against tumor and virus-infected cells. We recently found a NK subset in liver, which is markedly different from conventional NK cells, called liver-resident NK cells, occupying around 50% of all liver NK cells, with DX5-CD49a+ phenotype, developed within liver, classifying as “ILC1-like cell” recently by the field, however, the function of this subset is still obscure. As for liver works as an immunotolerant organ with high content of NK cells, it is important to study the immunoregulatory function of liver-resident NK cells. Our preliminary data demonstrated that liver-resident NK cells highly express membrane PD-L1 and TIGIT, and secret high level of IL-10, suggesting this NK subset reserves a potential of immune regulation. In this study, through comparison with conventional DX5+CD49a- NK cells, liver-resident NK cells are going to be extensively explored for “regulator” phenotype; after co-culture and in vitro blockade with anti-PD-L1 or anti-TIGIT Abs, the regulatory effects of liver-resident NK cells on PD-1+T cells or CD155+ DC will be shown, respectively; using immune cell-deficient mice and adoptive cellular transfer to hepatotropic virus-infected mice, the regulatory effect of liver-resident NK cells on anti-virus immune cells are further confirmed in vivo, for which the PD-1/PD-L1、TIGIT/CD155 and IL-10/IL-10R pathways for regulatory function of liver-resident NK cells will be explored in details. The results of this study will expand the knowledge of NK cell biology and helpful to explain the novel mechanisms of liver-related diseases.

NK细胞是异质性细胞群体，目前主要研究其对靶细胞的“自然杀伤”功能。我们近期揭示小鼠肝脏存在一群特有NK细胞，占肝脏总NK细胞约50%，具DX5-CD49a+独特表型，可能发生发育于肝脏本身，显示出与经典NK 细胞的诸多差异，最近被国际免疫学界归为ILC1-like细胞，其免疫学功能仍然不明。鉴于肝脏免疫耐受特性和高含NK细胞，发掘肝脏中具免疫负调功能的NK细胞是解读肝脏免疫耐受特性的重要环节。我们预实验结果表明这群NK细胞高表达PD-L1和TIGIT并高分泌IL-10，提示可能具备负调免疫应答的功能。本项目将集中研究肝脏特有NK细胞（DX5-CD49a+）中可能存在的Regulator亚群；通过体外共培养和PD-L1或TIGIT阻断实验，验证该肝脏特有NK细胞对PD-1+T细胞或CD155+DC细胞的负调效应；采用免疫细胞转输技术进一步验证该肝脏特有NK细胞对嗜肝病毒免疫应答的负调作用。

我们的前期研究发现小鼠肝脏存在一群肝脏特有NK（LrNK）细胞，占肝脏总NK细胞约50%，具DX5-CD49a+独特表型，显示出与经典NK 细胞（cNK）的诸多差异，鉴于肝脏的免疫耐受特性和高含NK细胞，发掘肝脏中具免疫负调功能的NK细胞是解读肝脏免疫耐受特性的重要环节，为此我们对这群肝脏特有NK细胞的功能进行了深入研究。结果表明：肝脏特有NK细胞具有免疫负调细胞的表型，在体外具有抑制T细胞增殖的能力，在体内具有抑制机体抗病毒免疫应答的功能。进一步研究证明肝脏特有NK细胞的这种抑制功能是通过PD-L1分子与T细胞的PD-1分子相互作用发挥抑制作用的。本研究揭示了肝脏驻留NK细胞具有负调T细胞抗病毒应答的功能及其分子机制，为肝脏免疫耐受的成因提供了新视角。