Abstract:

Objective To explore the dynamic changes of early stage immune responses in the skin of C₅₇BL/6 mice vaccinated with UV-attenuated Schistosoma japonicum. Methods The thickness of double pinnae was measured respectively in total 98 mice, then the mice were divided into two groups in average except 14 acted as the group of day 0 (naive). Each mouse was infected with 150 normal cercariae per pinna in Group One while each was vaccinated with 150 attenuated cercariae in Group Two. All mice were infected or vaccinated through double pinnae. On days l, 2, 4, 7,14, 21 after the exposure, seven mice were sacrificed respectively in each group and the thickness of pinnae was measured. Then, the exposed pinnae were removed and dealt as follows. The left sides were cultured and the supernatants were collected to detect corresponding cytokine while the right ones were cut open along longitudinal section. One halves were stained with HE to observe dynamic changes of inflammation and the other halves were dealt with immunohistochemistry to observe the expression of IL-12 and CDllc. Results Inflammation of the skins derived from mice infected with normal cercariae fell off gradually after it got to peak on day 7 and revived on the whole on day 21. However as the attenuated pinnae were concerned, the immune response did not get the strongest until day 14 and still intensive on day 21. There were more expressions of CDllc and IL-12 0n day 4 after the skins exposed to cercariae. Quantitative detection of cytokines secreted by cultured skin explants showed that IL-12 and IFN-Y were higher in group of mice vaccinated with attenuated cercariae than those in mice infected with normal cercariae in the early stage while IL-10 was on the other side. Conclusions Compared with the infection with normal cercariac, immune responses induced by attenuated cercariae are longer and more intensive. Although they can induce Th polarizing to different directions, it does not develop at the priming stage of immune.

Key words: Schistosoma japonicum, Attenuated cercariae, Pinna skin, Immune response

摘要：

目的 观察紫外线辐照致弱日本血吸虫尾蚴经耳廓免疫C₅₇BL/6小鼠后，小鼠皮肤组织早期免疫应答的动态变化。方法 98只小鼠测定双侧耳廓厚度后，14只作为0d组不感染／免疫，其余平均分为2组。一组经双侧耳廓分别感染正常尾蚴150条／耳，另一组经双侧耳廓分别免疫紫外线辐照致弱尾蚴150条／耳。感染／免疫后第1、2、4、7、14、21天分别剖杀2组小鼠各7只，测定耳廓厚度。取感染处的耳廓组织，左侧进行培养，收集上清检测相应细胞因子。右侧纵切为二，一半进行HE染色观察炎症反应；另一半应用免疫组化技术观察皮肤组织中IL-12和CDllc分子的表达。结果 正常尾蚴感染的小鼠皮肤炎症反应在第7天达到高峰后逐渐下降，第21天基本恢复；而辐照尾蚴免疫小鼠耳廓皮肤在第14天炎症反应才达高峰，第21天反应仍然十分强烈。尾蚴穿皮后第4天，组织中有较高水平的CDllc及IL-12分子表达。皮片培养细胞因子定量检测也显示：与Thl细胞应答相关的IL-12、IFN-Γ及Th2型因子IL-10早期在正常、辐照尾蚴差异无显著性。结论 和正常尾蚴相比，辐照致弱尾蚴诱导的皮肤免疫应答持续时间长、强度高，但两者诱导Th细胞向不同方向极化并不发生于免疫应答启动阶段。

关键词: 日本血吸虫；致弱尾蚴；耳廓皮肤；免疫应答