Biomphalaria glabrata: influence of calcium, lectins, and plasma factors on in vitro phagocytic behavior of hemocytes of noninfected or Schistosoma mansoni-infected snails.
In vitro phagocytosis of erythrocytes by hemocytes of B. glabrata, intermediate host of S. mansoni, is strongly influenced by calcium, several lectins, and plasma factors. Our results indicate that two different mechanisms of non-self-recognition in B. glabrata may occur: (1) In the presence of calcium, phagocytosis occurs in noninfected and in infected snails without involvement of any other substances, and hemocytes of schistosome resistant as well as those of susceptible snails are able to recognize and phagocytose the target cells. (2) In the absence of calcium, phagocytosis occurs if bridging molecules (heterologous lectins in our assays) were present for which effector and target cells possess binding sites or if target cells were plasma coated prior to the assays. In suspensions in homologous plasma, hemocytes of both snail strains, infected or noninfected, subsequently showed phagocytic activities of about 70-80%. Preincubation of target cells in homologous plasma resulted in similar high phagocytic activities of hemocytes even in the absence of plasma during the standard assay. In these assays, a significantly higher proportion of hemocytes of resistant snails phagocytosed plasma-opsonized erythrocytes, whereas hemocytes of susceptible snails internalized less erythrocytes per cell and needed 60 min to phagocytose at percentages equivalent to that of resistant hemocytes within 10 min. Preincubation of erythrocytes in resistant plasma significantly increased the subsequent phagocytic activity of susceptible hemocytes, whereas preincubation of erythrocytes in susceptible plasma decreased the phagocytosis level of resistant hemocytes.
Zelck
U
U
Zoologisches Institut und Zoologisches Museum, Universität Hamburg, Germany.
Becker
W
W
D000818:Animals; D001700:Biomphalaria / Q000276:immunology* / Q000469:parasitology; D002118:Calcium / Q000494:pharmacology; D006434:Hemocytes / Q000276:immunology; D037102:Lectins; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010949:Plasma / Q000502:physiology; D012550:Schistosoma mansoni / Q000502:physiology
D037102:Lectins; D002118:Calcium