The release of membrane antigens into culture by adult Schistosoma mansoni.

Antigens sharing determinants with surface membranes and soluble proteins of adult Schistosoma mansoni have been detected in culture media after incubation of radioactively labelled worms. The relative quantities of these antigens were measured with specific antisera raised in rabbits and with serum from an immune rhesus monkey. It was found that 12-16% of TCA-precipitable radioactivity in the culture medium consisted of membrane antigens and 6-8% consisted of antigens sharing determinants with proteins found in the soluble fraction of adult worms. Over half the membrane antigens were present in particulate form, while other antigens were present in solution. Surface labelling the adult worms with [125I]confirmed that some of the particles in the culture medium were derived from the surface membrane of the adult worm and electron microscope examination of such particles showed that large membrane fragments were present. These results support the hypothesis that antibodies against schistosome membrane antigens are induced by particulate membrane antigens released by the parasite.