We showed that infection with schistosomiasis alone significantly increased the levels of IFN-γ and IL-4 in the host serum, while pre-infection with toxoplasma further improved the increasing effect of IFN-γ and soluble worm antigen (SWA)-IgG2a level but decreased the level of IL-4 and anti- soluble egg antigen (SEA)-IgG1. The gene discussed is IFNG; the disease is infection.