牛乳腺炎无乳链球菌β溶血素对奶牛外周血液单核巨噬细胞吞噬功能的影响

Effect of the bovine Streptococcus agalactiae β-hemolysin gene on mononuclear phagocytes

目的探索奶牛乳腺炎无乳链球菌β溶血素对奶牛单核巨噬细胞吞噬功能的影响。方法利用牛淋巴细胞分离液从奶牛外周血分离获得单核细胞,经培养使其分化成巨噬细胞,利用牛乳腺炎无乳链球菌野生型菌株(BMSA1886βh)及牛乳腺炎无乳链球菌β溶血素基因敲除突变株(BMSA1886△βh)侵染巨噬细胞,通过吖啶橙染色法对其进行染色荧光显微观察,统计巨噬细胞对BMSA1886βh及BMSA1886△βh吞噬率差异。结果巨噬细胞对奶牛乳腺炎无乳链球菌野生型株的吞噬指数(1.16)和吞噬率(58%)显著低于其对与β溶血素突变株的吞噬指数(2.06)和吞噬率(80%),表明β溶血素可抑制巨噬细胞的吞噬作用。结论牛乳腺炎无乳链球菌β溶血素对奶牛外周血液巨噬细胞有一定的抑制作用,被吞噬的野生型无乳链球菌在巨噬细胞内的存活率较突变株相对较高。

Objectives To explore the effect of Streptococcus agalactiae β-hemolysin on macrophage recognition and immune regulation. Methods Mononuclear cells isolated from bovine peripheral blood were differentiated into macrophages, and macrophages were infected with a wild-type strain of S. agalactiae(BMSA1886βh) and a β-hemolysin gene knockout mutant(BMSA1886△βh). Both host macrophages and bacteria with acridine orange staining were observed using fluorescence microscopy. Results The phagocytic index of macrophages against the wild-type strain of Streptococcus agalactiae was 1.16, and the rate of phagocytosis was 58%. The phagocytic index of macrophages to the β-hemolysin mutant strain of Streptococcus agalactiae was 2.06, and the rate of phagocytosis was 80%. Results indicated that β hemolysin inhibits macrophage phagocytosis. Conclusion β-hemolysin inhibits the macrophage phagocytosis of S. agalactiae and it also increase the survival rate of S. agalactiae in macrophages.