Antibody isotype responses to the Schistosoma mansoni schistosomulum in the CBA/N mouse induced by different stages of the parasite life cycle.

During infection with Schistosoma mansoni the extent and nature of immune reactions against schistosomula may be influenced by responses to cross-reactive antigens in eggs or adult worms, and there is now extensive evidence for cross-reactivity between the different stages of the parasite life cycle. In this study IgM and IgG subclass antibodies produced in (CBA/N x Balb/c) F1 male and female mice were measured over a period of time following exposure to a chronic infection, to unisexual male cercariae or to irradiated larvae. Antibody levels were also measured following immunization with antigen preparations derived from adult worms, schistosomula or eggs. (CBA/N x Balb/c) F1 male mice exhibit an X-linked immune deficiency which results in an inability to respond to T-independent (TI) type 2 polysaccharides. Isotype levels were measured by ELISA to detergent-soluble schistosomulum antigen. Results showed that antigens on the different stages of the parasite life cycle have a qualitative influence on the antibody response to the larval surface, and that T-independent type 2 polysaccharides, particularly abundant in egg, exhibit antigen-directed isotype restriction in the form of IgM and IgG3 antibodies.