Genetic control of immune responses to Schistosoma japonicum antigen.

A high-titre IgE-antibody response to Schistosoma japonicum antigen (Sj) is obtained if helper T cells are appropriately induced by the infection. The antibody responses were found to be regulated by a gene(s) linked to the major histocompatibility complex. Strains of H-2a and H-2k haplotypes were high responders, whereas H-2d, H-2b and H-2s strains were not. Results obtained by using intra-H-2 recombinant strains suggested that the immune-response (Ir) gene was mapped in the I-E subregion, although a possibility of the presence of complementary genes was not excluded. Interestingly, in low responders such as BALB/c mice, Sj-specific carrier effect could be demonstrated when mice were infected with S. japonicum before challenge immunization with dinitrophenylated Sj (DNP-Sj). Moreover, BALB/c as well as C3H/He was a high responder to Sj in proliferation of peritoneal exudate T-lymphocyte enriched cells in vitro, whereas B10.S was not. Based on these observations, possible roles of Ir genes in immune responses to Sj are discussed.