SCHISTOSOMA-MANSONI MODULATION OF PHAGOCYTOSIS IN BIOMPHALARIA-GLABRATA

Both short-term (3 hr) exposure of Biomphalaria glabrata snails (M-line and 13-16-R1) to Schistosoma mansoni (PR1) miracidia and in vitro incubation of parasite sporocysts with host hemolymph components altered host phaocytic ability. Hemocytes obtained from susceptible (M-line) snails that had been exposed to parasite miracidia for 3 hr showed reduced levels of phagocytosis of yeast cells in vitro compared to hemosytes from unexposed individuals . Incubation of whole hemolymph with sporocyst in vitro also reduced yeast phagocytosis in this suscpetible strain. In contrast, resistant (13-16-R1) hemocytes showed increased levels of yeast pphagocytosis after in vitro incubation with the parasite, and the opsonic properties of 13-16-R1) plasma were greater after e exposure of snails to miracidia. These strain-specific effects of S. mansoni on host hemocyte phagocytosis and plasma opsonization were seen only when both plasma and hemocytes were present at the time of exposure to the parasite.