LECT2是一个重要的脊椎动物细胞因子，前期研究揭示哺乳动物LECT2能激活巨噬细胞，提高细菌性败血症小鼠的存活率，鱼类LECT2与其抗菌免疫相关，但功能与作用机理尚不清楚。本项目旨在研究香鱼LECT2是否通过CD209样受体调控巨噬细胞功能，参与整体抗菌免疫能力。拟通过向细菌感染香鱼体内注射LECT2检测存活率、组织载菌量、组织病理和细胞因子表达变化，证实LECT2对香鱼整体的免疫保护作用，解明其作用机制是通过抑制早期炎症或是促进保护性免疫；通过体外细胞培养，研究LECT2处理后香鱼巨噬细胞基因表达、吞噬和杀菌能力变化，证明LECT2激活巨噬细胞功能，解明香鱼LECT2保护性免疫的细胞机理；通过RNA干扰和抗体封闭阻断巨噬细胞CD209样受体，证实CD209样受体介导LECT2激活香鱼巨噬细胞功能。通过项目实施，有望揭示LECT2在鱼类抗菌免疫反应中的保护作用机制。

Leukocyte cell-derived chemotaxin 2 (LECT2) is reported to be an important cytokine in vertebrate. Previous studies have shown that LECT2 could activate macrophages to improve the survival of septic mice. However, the functions of LECT2 in fish immune response remain unclear. In this study, we aim to investigate whether LECT2 protects Plecoglossus altivelis against bacterial infection by activating macrophages via the CD209-like receptor. By observing the survival, bacterial killing, tissue pathological section and cytokine expression in infected fish treated with LECT2, we will illustrate whether LECT2 effect is dependent on reducing the exaggerated inflammatory response or improving the protective immunity. By using primary cultured head kidney-derived macrophages, we will investigate the activation effect of LECT2 on macrophages including the alterations of gene expression, cytokine secretion, phagocytosis and bacterial killing to illustrate the cellular mechanism of the immune protection effect of LECT2. By using RNA interference and neutralizing antibody block techniques, we will verify that CD209-like receptor is the functional receptor of LECT2 on macrophages. This work will elaborate the protective mechanism of LECT2 on fish infected with bacteria.