Abstract: Indirect ELISA was employed to monitor the serum anti-UEA(urea soluble egg antigen of Schistosoma japonicum )antibody level of mice immunized by a. UEA pulsed macrophage (M + ); b. Cultural supernatant of M+; c. paraformaldehyde fixed M(P -M)pulsed with UEA; d. Ammonium chloride treated M0 (NH4Cl-M0) pulsed with UEA, e. P -M0 pulsed with trypsin digested UEA (T-UEA ); f. NH4C1-M pulsed with T-UEA. The normal M its supernatant and the culture media RPMI 1640 acted as the negative control.The results showed : 1. Serum anti-UEA antibody levels of mice immunized by a and b raised markedly, indicating that the immunogenicity of UEA might be kept up after M processing and the antigenic message could be transferred either by the M+ or by its supernatant; 2. Mice immunized by c and d gave similar results, but the anti-UEA antibody level of the former was higher than that of the latter, suggesting that polyformaldehyde could not alter the UEA binding site on the surface of M; 3. In the case of mice immunized by e and f , the antibody levels were much lower than that of mice immunized by c and d, suggesting that UEA binding sites on M surface as well as UEA immunogenicity could be changed by trypsin.