Toll样受体7敲除对日本血吸虫感染早期免疫应答的影响

Effect of Toll-like Receptor(TLR) 7 Deficiencies on the In Vivo Immune Response against Schistosoma japonicum

目的探讨Toll样受体7(TLR7)敲除对日本血吸虫感染小鼠免疫应答的影响。方法野生型C57BL/6小鼠(WT,n=9)和TLR7-/-敲除小鼠(TLR7-/-,n=9)以腹部贴片法感染日本血吸虫尾蚴(20条)。感染后42 d处死小鼠,以胸主动脉灌注法收集虫体(n=6),并取肝脏进行虫卵计数;分别取WT、TLR7-/-未感染小鼠,WT、TLR7-/-感染小鼠的脾脏(n=3),制备脾细胞悬液;加入日本血吸虫虫卵(250个/ml)刺激72 h,ELISA法检测γ干扰素(IFN-γ)、肿瘤坏死因子α(TNF-α)、白细胞介素4(IL-4)和IL-10水平。结果感染后42 d,WT组平均虫荷数为(10.5±3.3)条,每克肝卵数为(38 251.9±4 891.5)个;TLR7-/-组平均虫荷数为(9.8±5.2)条,每克肝卵数为(38 160.9±3 341.0)个,两组间差异无统计学意义(P>0.05)。在未感染的情况下,TLR7-/-小鼠脾细胞上清液中的IL-10[(1702.6±572.3)pg/ml]和IL-4[(59.5±10.1)pg/ml]水平远高于WT组小鼠[(595.2±386.3)和(8.3±0.9)pg/ml](P<0.05,P<0.01)。感染后42 d,TLR7-/-组小鼠脾细胞上清液中的TNF-α[(43.7±9.8)pg/ml]和IFN-γ[(215.2±35.4)pg/ml]水平低于WT组[(63.4±22.9)和(383.5±253.3)pg/ml],而IL-4[(63.9±33.9)pg/ml]水平高于WT组小鼠[(23.3±11.5)pg/ml],但TLR7-/-组与WT组间的差异无统计学意义(P>0.05)。结论 TLR7-/-小鼠在未感染的状态下偏向Th2反应,不影响感染日本血吸虫6周后的免疫应答。

Objective To explore the toll-like receptor 7 knocked out（TLR^7-/-） mice immune response against Schistosoma japonicum. Methods C57BL/6 mice（WT） and TLR^7-/- mice（TLR^7-/-） were infected with 20 S. japonicum cercariae via shaved abdomen. There were nine mice in each group. At 6 weeks post-infection, mice were sacrificed. Adult worms were harvested by perfusion of the portal venous system, and the number of adult worms was determined. At the time of perfusion, livers were collected, weighed, and digested overnight with 5% potassium hydroxide, and eggs were counted. In addition, spleens were aseptically harvested when WT and TLR^7-/- mice were sacrificed at day zero and 6 weeks after S. japonicum infection. After 72 hours of the co-culture with or without S. japonicum eggs, the culture supernatants were collected for cytokine assays by ELISA assay. Results At 6 weeks after infection, there was no significant difference in number of worms [（10.5±3.3） vs （9.8±5.2）] and eggs per gram of liver tissue [（38 251.9±4 891.5） vs （38 160.9±3 341.0）] between WT and TLR^7-/- mice. As for Th1/Th2 cytokine secretion from spleen cells, the levels of TNF-α[（43.7±9.8） pg/ml] and INF-γ[（215.2±35.4） pg/ml] from TLR^7-/- infected mice were lower than those of WT infected mice[（63.4±22.9） pg/ml, （383.5±253.3） pg/ml]. For Th2 cytokines detection, the production of IL-10 [（1 702.6±572.3） pg/ml] and IL-4 [（59.5±10.1） pg/ml] from TLR^7-/- mice were higher than those of WT mice [（595.2±386.3）pg/ml,（8.3±0.9）pg/ml]（P〈0.05, P〈0.01）, while IL-4 level [（63.9±33.9） pg/ml] from TLR^7-/- infected mice was higher than those of WT infected mice[（23.3±11.5） pg/ml]. Conclusion TLR^7-/- mice has a dominant Th2 response under the normal state. The absence of TLR7 does not influence the immune response against S. japonicum infection at 6 weeks post-infection.