Plasma components which mediate cellular defences in the gastropod mollusc Biomphalaria glabrata

Blood plasmas from certain strains of Biomphalaria glabrata are known to have components which facilitate a hemocyte-effected cytotoxic response against encapsulated Schistosoma mansoni sporocysts. The possible identity of the factor(s) has been investigated. Sporocysts placed in snail plasma rapidly acquire a wide variety of host plasma antigens, at least some of which are displayed on the parasite surface. Plasmas from strains of snail resistant to the parasite agglutinate fixed sporocysts, while plasmas from susceptible strains fail to do so. Fixed sporocysts incubated in plasma bind selectively a subpopulation of plasma antigens; some are bound uniquely in resistant plasma. Another resembles a hemagglutinin from snail plasma. These and other recently acquired data are discussed in light of increasing evidence for defensive roles of multivalent lectins.