金黄葡萄球菌肠毒素A诱导的免疫应答

The immune responses induced by recombinant

目的研究超抗原金黄葡萄球菌A型肠毒素（SEA）在体内诱导的体液免疫反应、T淋巴细胞增殖及免疫无应答的规律和作用。方法利用重组SEA蛋白免疫小鼠，酶联免疫吸咐试验（ELISA）检测特异性抗体及其亚类水平，观察两者的产生过程及变化规律。RT—PCR反应检测免疫后小鼠脾脏内细胞因子的mRNA表达水平，ELISPOT法检测rSEA对脾细胞分泌IFN-γ能力的影响，流式细胞术检测T淋巴细胞表面抑制性受体PD-1的表达。结果BALB／c小鼠在低剂量的rSEA初次免疫后2周，即产生了高水平的特异性抗体，此时体内以体液免疫应答为主，IgG2a／IgG1〈1；而在免疫早期，Th1型细胞因子的mRNA表达水平高于Th2型，以细胞免疫应答为主。短时期内进行再次免疫后脾细胞的IFN-1分泌频率显著下降；流式细胞仪在rSEA激活的T淋巴细胞表面检测到了PD-1（programmed death-1）分子的表达，其表达量随时间及免疫次数增加。结论超抗原SEA初次免疫即能引起强大的体液免疫应答与细胞免疫应答；再次免疫引起了免疫无应答，这与PD-1介导的抑制作用增强有关。

Objective To observe the effects of superantigen-induced humoral immunity, T cells proliferation and anergy in vivo. Methods ELISA was used to detect the specific antibodies IgG, IgG1 and IgG2a in serum of mice induced by recombinant staphylococcal enterotoxin A （rSEA）. The mRNA expression of cytokines in spleen cells was examined by RT-PCR. Antigen-specific IFN-γ, production was assayed using the ELISPOT kit and the expression of inhibitory receptor PD-1 was determinated by FCM. Results BALB/c mice intraperitoneal immunized with the rSEA producted high level of rSEA-special antibody and induced T lymphocyte proliferation which has differentiation with type Ⅰ or Ⅱ T cells. The average frequency of specific IFN-γ producing cells in spleens did not increase when immunized again with rSEA in a short time. The expression of PD-1 molecular on spleen T cells were different in each group. Conclusion Humoral immunity and T cells proliferation can be induced significantly by rSEA. The expression of PD-1 is likely responsible for the induction and maintenance of T cells anergy induced by superantigen rSEA.