CONICET | Buscador de Institutos y Recursos Humanos

Invertebrate hemocytes are concerned with innate defense mechanisms such as phagocytosis, pathogen encapsulation and lysis of foreign cells. Three hemocyte morphological ?types? are found in the circulation of this snail, which have been identified as hyalinocytes, agranulocytes and granulocytes, on the basis of their light and electron microscopy characteristics. Nevertheless, the functional roles of each of these cells remain unexplored in P. canaliculata. We have developed a flow-cytometric method to sort three hemocyte subpopulations from freshly withdrawn hemolymph, which correspond predominantly to the three hemocyte morphological ?types?, and which will allow us to study their functional properties. Here we report an assessment of the phagocytic ability of the sorted hemocyte subpopulations, as compared between them and with the whole population of circulating hemocytes. Both unsorted and sorted hemocytes were exposed to fluorescent latex beads (10:1 beads/hemocyte) for one hour. Cell associated fluorescence was used to determine the percent of phagocytizing hemocytes (phagocytic index) in each sample. Hyalinocytes showed a phagocytic index statistically higher than that of agranulocytes and granulocytes (ANOVA, Bonferroni?s multiple comparison test; p < 0.05, n = 6), and which was not statistically different from that of the unsorted circulating hemocytes. Interestingly, bead exposure resulted in generalized granulocyte degranulation, even though only some of these cells showed phagocytic activity. Also, degranulated cells showed nuclear condensation, which is suggestive of induction of cell death. It is concluded that hyalinocytes are the main phagocytes in the circulation and that granulocytes release their granules in response to foreign particles. Degranulation might be related to the release of antimicrobial substances.