Abstract：To investigate the related mechanism of regulatory T cells(Tregs) to regulate the Th1 immune responses in the early infection with Plasmodium yoelii 17XL,1×106 virulent P.yoelii 17XL parasitized erythrocytes injected intraperitoneally to infect BALB/c mice injected with anti-CD25,mAb and the control mice.The ratio of the infected RBC was counted.On days 0,3 and 5 post infection,the dendritic cells(DCs) from spleen were purified by magnetic separation and cultured in vitro.The levels of IFN-γ in the supernatants of the cultured splenocytes and IL-12 in the supernatants of the cultured DCs were assayed with ELISA assay and the content of NO in the splenocyte supernatants was detected by Griess's method.It was demonstrated that the levels of both IFN-γ and NO were significantly increased in the supernatants of cultured splenocytes from two groups of BALB/c mice,but those in the control mice were comparatively lower than those of mice injected with anti-CD25 mAb.The level of IL-12 in supernatants of cultured DCs of the anti-CD25 mAb injected mice reached its peak on day 3 post-infection and maintained at a high level 5 on day after infection.In contrast,the level of IL-12 in the supernatants of cultured DCs of the control mice only showed significant increase on day 3 postinfection.These results suggest that Tregs might inhibit the effective development of the TH1 immune response at the early stage of P.yoelii 17XL infection in BALB/c mice through inhibition of secreting IL-12 from DCs.
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