FREEZE-FRACTURE STUDY OF IMMUNE-INDUCED SCHISTOSOMA-MANSONI MEMBRANE-ALTERATIONS .1. COMPLEMENT-DEPENDENT DAMAGE IN THE PRESENCE OF ANTISERA TO HOST ANTIGENIC DETERMINANTS

Some early events of membrane alteration were described by the freeze-fracture technique in an in vitro killing system of Schistosoma mansoni by rat immune serum directed against host proteins. The recognition of host determinants on the surface of the parasite leads to a reordering in the hydrophobic domain of the tegumental outer membrane. The constant formation of aggregates of preexisting intramembranous particles (or tetrads) was mediated by thermostable antibodies. The killing of the adult worms and the accumulation of tetrads within the membrane lining the tegumental pits were observed in the presence of heat-labile factors which are presumed to be complement. Without the action of C components, a flow of tetrads to the tegumental spines was detected. The multilaminate vesicles present in the tegument and membranes from basal lamina evaginations appear to fuse with the cytoplasmic membrane of side channels. The significance of these findings is discussed in relation to a possible ability of the worm to repair its membrane and adapt itself to a new environment. © 1979 Academic Press, Inc.