EXPRESSION OF CELL-SURFACE LECTINS ON HEMATOPOIETIC PROGENITOR CELLS

The expression of lectins on the surface of the murine multi-myeloid p rogenitor cell line FDCP-Mix, and the human leukaemic cell line KG1, w as assessed and compared to the pattern of lectin expression observed on human bone marrow mononuclear cells. Using flow cytometry, cell-sur face lectins were identified by their ability to recognise fluorescein isothiocyanate-labelled neoglycoproteins. Both cell lines recognised neoglycoproteins expressing alpha-D-glucose and alpha-D-galactose resi dues. Inhibition studies suggested that recognition of these neoglycop roteins was via two independent receptors, each displaying characteris tic sugar-binding properties. The CD34+ population of bone marrow mono nuclear cells, identified by positive staining with the anti-CD34 anti body QBend10, were shown to interact with alpha-glucose-, alpha-galact ose- and alpha-D-mannose-expressing neoglycoproteins. Similarly, bindi ng of these probes to lymphocyte and monocyte sub-populations of CD31- bone marrow mononuclear cells was observed. In contrast, CD34- granul ocytic cells did not appear to recognise these probes. It is suggested that the alpha-D-galactose binding activity observed for both cell li nes and the alpha-D-galactose and alpha-D-mannose binding activity obs erved for bone marrow mononuclear cells represent expression of the co mponent polypeptides of the previously reported galactosyl/mannosyl re ceptor. The glucosyl-specific receptor, observed on both cell lines an d on bone marrow mononuclear cells, has not been reported previously. It is suggested that this receptor may mediate glucose transport or ce ll adhesion through recognition of glucosyl-containing compounds such as heparan sulphate.