Identity of antigens in adult tegument, gut, egg and cercaria of Schistosoma japonicum by immunofluorescent study.

Specificity of antigens in the different stages and tissues, i.e., gut and tegument of the adult worm, cercaria and egg of Schistosoma japonicum (Sj) were examined by the direct and indirect immunofluorescent antibody method with various immune rabbit sera. Antigenic properties were completely different between gut of adult worms and egg. Cross-reactions, however, occurred among egg, tegument and stroma of adult worms. This cross-reacting antigen in tegument appeared to be unstable against formalin fixation and heating. Furthermore, the antigens in the egg were definitely shared by testes of adult male worms and also by cercaria. On the other hand, the antigenicity in cercaria against anti-adult antibodies was rather low. Cross-reactions with immune sera against the parasites other than S. japonicum were lowest in S. japonicum gut. The antigen in tegument was especially sensitive to anti-Sj adult immune sera, but distinctly less to sera from S. japonicum infections. The antigen in tegument seemed to be more specific in detecting antibodies produced by immunization than those appearing after infection.