细胞毒性T淋巴细胞相关蛋白4在日本血吸虫免疫逃避中的作用及其机制研究

Effect and mechanism of CTLA-4 on the immune evasion of Schistosoma japonicumin mice

目的探讨细胞毒性T淋巴细胞相关蛋白4(CTLA-4)在日本血吸虫免疫逃避中的作用及其机制。方法雌性BALB/c小鼠随机分成3组,即正常对照组、感染对照组和抗CTLA-4单克隆抗体(Anti-CTLA-4mAb)组。各感染组每只小鼠经腹部皮肤感染日本血吸虫尾蚴40条,感染2周后,Anti-CTLA-4mAb组每只小鼠连续3d腹腔注射300μg anti-CTLA-4mAb,对照组注射等体积的PBS。感染后6周杀鼠冲虫,计数每只小鼠虫荷及每克肝脏虫卵数。流式细胞术检测各组小鼠脾淋巴细胞中调节性T细胞(CD4+CD25+Tregs)百分比。ELISA法检测各组小鼠脾淋巴细胞培养上清中细胞因子IFN-γ、IL-4、IL-5和IL-10的含量。肝组织石蜡切片HE染色观察感染组小鼠肝脏虫卵肉芽肿病理变化。结果 Anti-CTLA-4mAb组减虫率为18.99%,脾淋巴细胞中CD4+CD25+Tregs百分比显著升高(P<0.05)。Anti-CTLA-4mAb组脾细胞培养上清中细胞因子IFN-γ、IL-4、IL-5和IL-10的含量均高于感染对照组,肝脏虫卵肉芽肿直径较感染对照组明显增大。结论 AntiCTLA-4mAb使用同时增强Th1型和Th2型免疫反应,有利于机体清除日本血吸虫但以损伤机体为代价。研究结果提示宿主CTLA-4利于日本血吸虫免疫逃避。

In order to explore the effect and mechanism of cytotoxic T lymphocyte-associated protein 4 （CTLA-4） on the immune evasion of Schistosoma japonicurn （S. japonicum） in mice, the 18 female BALB/c mice were divided randomly into 3 groups： normal control, infected control and anti-CTLA-4 mAb treated group. Each mouse in infected control and anti-CTLA- 4 groups was challenged with 40 cercarie of S. japonicum. Mice in anti-CTLA-4 mAb group were treated with 300μg of anti- CTLA-4 mAb for 3 days consecutively, equal volume PBS as control. At 6 weeks post-infection, all mice were succumbed to measure worm burden and eggs per gram liver. The levels of IFN 7, IL-4, II.5 and 1110 were detected by sandwich-ELISA. Flow cytometry was performed to measure the percentages of CD4＋ CD25＋ tregs in splenic cells. Liver sections were stained with bematoxylin and eosin to detect egg granuloma. The results showed that reduction rate of worm burden in anti CTLA-4 mAb group were 18.99%. Compared with that of control group, the percentage of CD4＋ CD25＋ Tregs was extremely higher in anti-CTLA-4 mAb group. The egg granuloma size in anti-CTLA 4 mAb group were extremely larger than those of infected control group, while the levels of IFN-7, IL-4, IL-5,IL-10 in anti-CTLA-4 mAb group were extremely higher than those of control group. It＇s indicated that anti-CTLA-4 mAb favors the host to clear S. japonicum by enhancing Thl type immune re sponse, but at the cost of elevated pathological damage by enhancing Th2 type immune response. It hints that CTLA-4 contrib ute to the escape of S. japonicum from the host immune responses.