新细胞因子FAM19A4在白色念珠菌感染中的功能及机制研究

Cytokines have important roles in the immune system. When the Candida albicans infection occurs, macrophages and immature DC play phagocytosis and killing function first, then Th1 and Th17 cells are activated. They produce IFN-γ and IL-17, which activate phagocytes further and play anti-infective functions. FAM19A4 is a novel cytokine identified by the strategy of Immuno-functional genomics in the Department of Immunology, Peking University. FAM19A4 is a classical secreted protein, has chemotactic activity on TNF-α-activited macrophages. Recombinant FAM19A4 can enhance the phagocytosis and ROS reaction of murine macrophages against zymosan both in vitro and in vivo. In DTH model, it can aggravate the footpad swelling and increase the secretion of IFN-γ and IL-17 of murine spleen cells. These results suggest that FAM19A4 may play essential roles in the anti-Candida albicans infections. Based on the above work, we will do further experiments to know its mechanism on murine macrophages and its effects on human phagocytes and DC with zymosan; to investigate its direct activity on Th1 and Th17 cells in vitro; to isolate and identify its receptor based on further chemotactic assay; to construct FAM19A4 transgenic mice and Fam19a4 knockout mice and analyze the phenotypes; then conduct experiments to observe its function in Candida albicans infection with the recombinant protein, TG and KO mice both in vitro and in vivo. Above all, this project is original and feasible with solid preliminary work. It would be helpful to strengthen the research on anti-fungal infections in China.

细胞因子具有重要的免疫功能。发生白色念珠菌感染时，巨噬细胞、未成熟DC等首先发挥吞噬和杀伤功能；启动Th1和Th17细胞活化，产生IFN-γ和IL-17，进而活化吞噬细胞，抵御白念感染。FAM19A4是北大免疫学系鉴定的新细胞因子，为经典分泌蛋白；具有趋化活性；在体内外均能增强小鼠巨噬细胞对zymosan的吞噬能力；在DTH 模型中促进Th1、Th17细胞产生IFN-γ、IL-17，提示其可能参与抗白念感染。因此，本项目将首先以zymosan为研究对象，深入分析FAM19A4对小鼠巨噬细胞的作用机制、对人吞噬细胞和DC的功能；明确其对Th1和Th17细胞的直接作用；在此基础上分离、鉴定其受体；构建TG和KO小鼠，分析表型；进而以白念为研究对象，利用重组蛋白、TG和KO小鼠开展体内外实验，研究FAM19A4在白念感染中的功能和作用机制。本项目前期工作充分，创新性强，可行性佳。

细胞因子在免疫系统中发挥重要作用。当感染发生时，巨噬细胞首先发挥吞噬功能，并伴随大量炎性因子的释放。FAM19A4是通过免疫基因组学筛选得到的新细胞因子。此研究表明，FAM19A可在早期时相促进人原代巨噬细胞吞噬zymosan的能力，表现为吞噬zymosan的细胞比例的增加以及单个细胞吞噬颗粒的能力增强，并伴随ROS的释放加剧。FAM19A4可大幅增强Akt的活化，但又通过促进p65的降解抑制NF-κB转录因子的活性，从而削弱由zymosan刺激引起的炎性因子的上调，同时也抑制p38和ERK1/2的活化。在我们构建FAM19A4转基因小鼠的过程中，由于发生了基因的随机整合，导致了鉴定的极大困难，因此构建失败。综上，FAM19A4作为一个新细胞因子，可以通过活化Akt促进巨噬细胞的吞噬，并通过抑制NF-κB通路影响炎性因子的上调。