Interactions between the plasma proteins of Biomphalaria glabrata (Gastropoda) and the sporocyst tegument of Schistosoma mansoni (Trematoda).

The tegumental surface of Schistosoma mansoni sporocysts is the site of both nutritive and immunological interactions with haemolymph cells and plasma of Biomphalaria glabrata, the schistosome intermediate host. Within minutes of being placed in host plasma, sporocysts acquire plasma antigens, and within 3 h host plasma antigens are present on the surface at near steady state. Though a wide variety of peptides is acquired, there is selection. Furthermore, some differences occur in the peptides acquired from the plasma of susceptible and resistant strains of snail. Acquired antigens are rapidly processed, and are predominantly undetectable in tegumental extracts after a few hours. In contrast, rabbit antibody on sporocysts remains in situ for at least 48 h, so under some conditions there is stable expression of certain tegumental antigenic determinants. These data, obtained using antibodies to snail plasma antigens and to sporocyst tegumental antigens, are discussed in the light of current ideas on the cellular and molecular basis of susceptibility and resistance in this host-parasite system.