Experimental research on immunoregulatory efficacy of IL-10 in Plasmodium yoelii infection

Objective To explore immunoregulatory efficacy of IL-10 in Plasmodium yoelii infection. Methods DBA/2 and BALB/c mice were infected by i.p. injection of P. yoelii 17XL parasitized RBC. Parasitemia of individual mice was monitored by the microscopic examination on blood smears stained with Giemsa, and the levels of IFN-γ and IL-10 in sera were detected by ELISA Kit. Results DBA/2 mice spontaneously recovered on day 21 post-infection, the levels of IFN-γ rose markedly on the 3rd day of post-infection (6 542 pg/ml), then decreased gradually, but was higher than uninfected mice until the 12th day. The levels of IL-10 in DBA/2 mice begin to rise on day 6 post-infection (248 pg/ml), and reached a peak level (980 pg/ml) on day 15 post-infection then declined. Parasitemia of BALB/c mice reached 57.5% on day 6 post-infection, and then all mice died within two days. The levels of IFN-γ in BALB/c mice rose transiently on day 3 post-infection (2 225 pg/ml), however, the raise of IL-10 levels was prominent from day 3 to day 6 after infection (410-432 pg/ml). Conclusion Too early and excessively secreted IL-10 can inhibit Th1 response of mice infected with P. yoelii 17XL, however, there is a close relationship between timely secretion of IL-10 and switch of Th1 to Th2 response.