Abstract: Vaccinated serum getting from mouse which vaccinated with irradiated cercariae of S.mansoni.After western blot,using the vaccinated mouse serum to do immunodetection of soluble antigens of adult worm of S.mansoni on nitroeellulose paper.The result appeared that vaccinated mouse serum recognized 21 KDa solubleantigen of adult worm of S.mansoni obviously.The antibody combined with 21 KDa soluble antigen of adult worm on nitrocellulose paper was eluted and using that antibody to do Enzyme-linked immunosorbent assay(ELISA)With soluble antigens of each stage in life history of S.mansoni,all of the results were positive.We conclude that 21 KDa soluble antigen of adult worm of S.mansoni is a defined antigen.This antigen is not stage specific,it is a common antigen of each stage in life history of this parasite.The results indicate that 21 KDa soluble antigen of adult worm of S.mansoni is a surface antigen.

Key words: Schistosoma mansoni, western blot, defined antigen