We investigated the roles of the crude antigen(CA) of Clonorchis sinensis and excretory secretory products (ESPs) in the polarization of Th1 and Th2 cells.Bone marrow-derived cells were generated from BALB/c mice and isolated into immature DCs;immature DCs were then treated with either CA (CA stimulated group),ESPs (ESPs stimulated group),LPS (positive control group) or PBS (negative control group) for 24 hours.Then the CD4+T cells were isolated from mouse spleen by using anti mouse-CD4 Microbeads,and further cocultured with stimulated DCs for another 72 hours.The purities of DCs and CD4+ T cells were evaluated by flow cytometry and the expressing levels of T-bet mRNA and GATA-3 mRNA were detected by real-time PCR.ELISA was used to detect the levels of IFN-γ and IL-4 cytokines in the supernatant.mRNA levels of T-bet and GATA-3 in the ESPs group were higher than those in PBS-stimulated group (P＜0.05).The concentrations of IFN-γ and IL-4 cytokines in the culture were increased in the ESPs group,compared with PBS stimulated group(P＜0.05).IFN-γ but not IL-4 was increased in CA group (P＜0.05).The results implied that CA might play a role in Th1 type immune response,and ESPs likely play roles in both Th1 and Th2 immune responses.