Abstract:In this experiment, the sera from different infection stages of rabbits with Schistosoma japonicum were used in IFA technique to study the antigen localization and its changes during the process of infection. It showed that in our experimental observation on paraffin mount section fixed with Rossman's fixative, the antigens of adult Schistosoma japonicum were localized at the gut wall, parenchyma and tegument, while the intensity of reaction in series was gut wall, parenchyma and tegument respectively. The fluorescent reaction could be observed in the male reproduction system such as testis, while none of fluorescent reaction in female reproductive system. The higher reaction intensity appeared in male worm, especially in parenchyma when compared with the female. In the observation on preparation in cryostat section. The most remarkable reaction occurred in the tegument, with weak reaction in parenchyma and almost negative reaction in gut wall. In the study of antigen localization of the eggs in the infected mice, the antigens were localized at egg shell, vitelline membrane, space between miracidium and egg shell, apical gland and lateral gland of the miracidium in the paraffin mount section at the fourth week, with occurrence of higher positive reaction in the apical and lateral gland. Hoeppli phenomenon was observed around the egg at the fifth week. In the cryostat section, the antigens also appeared at the fourth week, they were localized on vitelline membrane and egg shell.