Expression of cell-surface lectins on haemopoietic progenitor cells

The expression of lectins on the surface of the murine multi-myeloid progenitor cell line FDCP-Mix, and the human leukaemic cell line KG1, was assessed and compared to the pattern of lectin expression observed on human bone marrow mononuclear cells. Using flow cytometry, cell-surface 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 residues. Inhibition studies suggested that recognition of these neoglycoproteins was via two independent receptors, each displaying characteristic sugar-binding properties. The CD34+ population of bone marrow mononuclear cells, identified by positive staining with the anti-CD34 antibody QBend10, were shown to interact with alpha-glucose-, alpha-galactose- and alpha-D-mannose-expressing neoglycoproteins. Similarly, binding of these probes to lymphocyte and monocyte sub-populations of CD34- bone marrow mononuclear cells was observed. In contrast, CD34- granulocytic cells did not appear to recognise these probes. It is suggested that the alpha-D-galactose binding activity observed for both cell lines and the alpha-D-galactose and alpha-D-mannose binding activity observed for bone marrow mononuclear cells represent expression of the component polypeptides of the previously reported galactosyl/mannosyl receptor. The glucosyl-specific receptor, observed on both cell lines and on bone marrow mononuclear cells, has not been reported previously. It is suggested that this receptor may mediate glucose transport or cell adhesion through recognition of glucosyl-containing compounds such as heparan sulphate.