Killing of Schistosoma mansoni sporocysts by Biomphalaria glabrata hemolymph in vitro: alteration of hemocyte behavior after poly-L-lysine treatment of plastic, and the kinetics of killing by different host strains.

Behavior of hemocytes of the gastropod mollusc Biomphalaria glabrata was markedly changed on plastic by treatment of the substrate with 0.1 mg/ml poly-L-lysine compared to behavior on untreated plastic. On lysine, the cells showed minimal spreading, moved significantly faster, and formed aggregates. Cell-mediated cytotoxicity (CMC) assays were set up on the modified and untreated substrates to compare the killing capacities of B. glabrata hemocytes against Schistosoma mansoni sporocysts. Hemolymph from 1316-R1 (resistant) snails showed higher killing in lysine-treated wells; no significant difference in sporocyst mortality was observed in MO (susceptible) hemolymph between treated and untreated wells. The CMC assays on poly-L-lysine-treated plastic were used to compare the kinetics of parasite killing in hemolymph from 2 susceptible (MO, MRLc) and 2 resistant (1316-R1, 10R2) host strains. Marked differences could be observed between the two resistant snail strains, suggesting different mechanisms of parasite recognition, killing, or both.