Monoclonal antibody recognized hemocyte subpopulations in juvenile and adult Lymnaea stagnalis: functional characteristics and lectin binding

The mouse monoclonal antibody LS1 recognizes a membrane epitope present on circulating hemocytes of the gastropod mollusc Lymnaea stagnalis. In both juvenile and adult pond snails, LS1+ (LS1 positive) hemocytes have the morphology of immature cells. The percentage of LS1+ hemocytes is higher in juveniles (ca. 39%) than it is in adults (ca. 14%). Functional characteristics of LS1+ hemocytes and lectin binding to these cells were studied. In both age groups, the proliferative activity, as measured by the incorporation of deoxybromouridine, is much higher for LS1+ hemocytes than it is for LS1- (LS1 negative) cells. LS1+ hemocytes are phagocytically less active and have a lower lysosomal enzyme (peroxidase) content as compared to hemocytes that lack the epitope. Histochemical staining of the total population of circulating hemocytes shows that the lectins DBA, BS-l-A4 and BS-l-B4, PNA, SBA and ECA do not react with the hemocytes. LTA, APA, WGA, Con A and LCA bind to all hemocytes. RCA and STA recognize surface carbohydrate moieties present on subpopulations of hemocytes only. The LS1+ hemocyte population virtually lacks the carbohydrate residues recognized by STA, whereas the LS1- population never shows binding of RCA. Our results support the findings that the LS1 epitope is a membrane marker of less differentiated hemocytes in both juvenile and adult L. stagnalis. Furthermore, they suggest a correlation between the presence of the LS1 epitope and the absence of STA binding, whereas absence of the LS1 marker may correlate with the presence of a sugar recognized by RCA.