CD8+T细胞促进肝脏驻留NK细胞成熟和功能及其分子机制

Nature killer (NK) cells are important lymphocytes of the innate immune system. As an organ with predominant innate immunity, the liver contain high proportion of NK cells which are heterogeneous. The investigation by our team and other groups suggest that the liver have a specific NK cells subset, termed liver-resident NK cells, which are different from conventional NK cells and other tissue resident NK cells in terms of phenotype, transcriptional factor regulation and function. Although research into the developmental origin and transcriptional regulation of liver resident NK cells have been well investigated, the signals guiding the differentiation and function of liver resident NK cells are not well understood. Our recent data shows that liver resident NK cells are divided into different stages of maturation, just like conventional NK cells in the peripheral blood. Moreover, CD8+T cells and IFN-γ have the capacity to induce the maturation and activation of liver resident NK cells in the steady state. Thus, to explore the molecular mechanisms of the development pathway of liver resident NK cells, in this study, the phenotype and function of liver resident NK cells during mouse ontogeny will be investigated to prove the different developmental stages of liver resident NK cells. Moreover, T cells depletion and adoptive transfer will be conducted to evaluate the subset of CD8+T cells that regulating the maturation and function of liver resident NK cells. At last, we will use cytokines knockout mice, antibody blocking, cytokines overexpression in the liver and cell-cell contact assays to investigate the molecular mechanisms of liver resident NK cells regulation by CD8+T cells, thereby clearly clarifying the cells and signals regulating the maturation and function of liver resident NK cells and serving as a paradigm for the study of other tissue resident NK cells.

自然杀伤（NK）细胞是固有免疫系统重要成员。肝脏作为天然免疫优势器官，含有高比例且具异质性的NK细胞。近期我们的研究发现，肝脏存在一群特殊的肝脏驻留NK细胞亚群，在表型、转录调控和功能上不同于外周循环经典NK及其他组织驻留NK细胞，但目前对调控其发育和功能的细胞及信号分子的研究甚少。我们前期研究显示与经典NK细胞类似，肝脏驻留NK细胞亦可分为不同的成熟阶段；且CD8+T细胞及IFN-γ均能促进肝脏驻留NK细胞发育成熟及功能分子的表达。为深入探究肝脏驻留NK细胞的发育成熟过程及其机制，本项目拟首先揭示肝脏驻留NK细胞的不同成熟阶段；利用缺陷鼠观察CD8+T细胞对肝脏驻留NK细胞发育阶段的影响，探究发挥关键调控作用的CD8+T细胞亚群；体内外实验验证CD8+T细胞对肝脏驻留NK细胞调控的分子机制；从而率先阐明调控肝脏驻留NK细胞成熟和功能的细胞及信号分子，为其他组织驻留NK细胞的研究提供范例。

肝脏作为天然免疫优势器官，含有高比例的自然杀伤（NK）细胞，我们之前的研究发现肝脏存在一群特殊的肝脏驻留NK（Liver resident NK, LrNK）细胞亚群，在表型、转录调控和功能上不同于外周经典NK，但目前对调控其发育成熟分子机制的研究甚少。通过本项目的研究发现CD8+T细胞缺失时，不成熟CD27+LrNK细胞亚群比例增加并且细胞毒活性受损，但是回补CD8+T细胞能够促进LrNK细胞的成熟，而阻断CD70和CD27的配受体相互作用，CD8+T细胞对LrNK细胞的促成熟作用消失，从而揭示了CD8+T细胞可通过CD70-CD27促进LrNK细胞的成熟及功能。同时在对疾病模型的探索中发现，HCC病人LrNK细胞的成熟与CD8+T细胞的活化成正相关；另外，我们也发现在2型糖尿病（T2DM）患者体内，NK细胞数量减少并且高表达抑制性受体Tim-3，Tim-3的高表达使得NK细胞功能受损并促进其凋亡。T2DM患者CD8+T细胞及单核细胞都高表达Tim-3的配体Galectin9，这就为CD8+T细胞通过Galectin-9-Tim-3相互作用负调NK细胞功能提供可能性。综上所述，我们的研究显示CD8+T细胞通过CD70-CD27作用促进LrNK细胞成熟，可能通过Galectin-9-Tim3相互作用抑制NK细胞功能，提示CD8+T细胞对NK细胞发育和功能调控具有复杂性。