Phagocytosis of latex beads by Biomphalaria glabrata hemocytes is modulated in a strain-specific manner by adsorbed plasma components

Abstract

Circulating phagocytes of the mollusc Biomphalaria glabrata help determine the fate of invading Schistosoma mansoni larvae. In mediating cytotoxicity against this trematode parasite, phagocytic hemocytes may interact with unidentified plasma components. In this study, positively and negatively charged latex beads were coated with plasma for use in in vitro phagocytosis assays. Hemocytes from S. mansoni-susceptible and -resistant strains of B. glabrata were tested for their ability to internalize beads coated with homologous and heterologous plasma components. Electrophoretic analysis showed that differences in the plasma polypeptides adsorbed to latex beads were charge-related, but no consistent strain-specific differences were detected. Hemocytes from a susceptible strain phagocytosed negatively charged latex pretreated in plasma form a resistant strain of snail at a higher rate than beads treated in plasma from the susceptible strain. Pretreatment of susceptible hemocytes with resistant plasma reduced subsequent phagocytosis of beads coated with resistant plasma, consistent with blocking of receptors on the susceptible hemocytes with resistant strahl plasma components. Exogenous lectins detected no differences in the carbohydrates on beads coated with plasma from either snail strahl. However, strain differences in endogenous lectins are suggested by differential binding of neoglycoproteins to plasmacoated beads. The plasma components) responsible for the differential phagocytosis of beads treated in the two plasma strains by hemocytes from the susceptible strahl of B. glabrata remain(s) to be identified.