Newly transformed schistosomula spontaneously lose surface antigens and C3 acceptor sites during culture

The binding of rat anti-schistosome antibody and rat C3 to the surface of newly transformed schistosomula of S. mansoni was measured by quantitative immunofluorescence during the first 48 hr of their development in vitro. Schistosomula, cultured in media either with or without serum, lost antibody or C3 from their surface exponentially with a halftime of 5 hr for both labels. The loss of the surface molecules is seen in parasites that are labeled and then cultured as well as in parasites cultured and then labeled, indicating that the labeling procedure itself is not inducing the observed change. This immunochemical modification in the schistosomulum surface appears to be independent of host molecule adsorption and intrinsic to the development of the parasite.