Artificially transformed schistosomula of Schistosoma mansoni: mechanism of acquisition of protection against antibody-mediated killing.

: Incorporation of labelled amino acid into tegumental proteins and acquisition of protection by schistosomula against antibody-mediated killing in vitro were simultaneously stimulated by serum factors and inhibited by puromycin. Comparison of polyacrylamide gel electrophoresis patterns with fluorographic autoradiography indicates that the majority of proteins in the parasite tegument were labelled with the isotope after incubation for 3 h. No new, clearly defined band was observed in the autoradiography pattern. During this period a decreasing susceptibility of the schistosomula to antibody plus complement was observed. Quantitative fluorescence assay shows that schistosomula insensitive to antibody plus complement were still able to bind the same amount of antibody as the unprotected parasites. Pre-culture of schistosomula in the presence of inactivated normal rabbit serum also decreased the susceptibility of the parasites to the in vivo killing mechanism.