Acquired resistance to Schistosoma japonicum in IgE-deficient SJA/9 mice immunized with irradiated cercariae.

Participation of IgE in protective immunity against Schistosoma japonicum was examined by comparing congenital IgE-deficient SJA/9 and IgE-producing SJL/J mice. Mice immunized with 100 irradiated cercariae 7 weeks previously were infected with 50 live cercariae. In SJL/J mice at 40 days after infection, a 3-to 4-fold increase of total IgE levels and anti-S, japonicum egg IgE antibody production were observed with no significant difference between immunized and nonimmunized mice. IgE was not detected in SJA/9 mice throughout the experiments. Protective immunity evaluated by recovery of adult worms was found in SJA/9 mice and was comparable to that of SJL/J mice. These results suggest that acquired immunity in mice with irradiated cercariae of S. japonicum was not dependent on IgE in these strains of mice.