Lectin binding and uptake in human (myelo)monocytic cell lines: HL60 and U937

The terminal carbohydrate residues of the human (myelo) monocytic cell lines HL60 and two subclones of U937 were investigated by the use of lectins. Several terminal carbohydrate residues, including N-acetylglucosamine and carbohydrates of the complex type, were detected on all three cell lines. Except for galactose residues, the two subclones of U937 had almost identical terminal carbohydrate residues. The differences between the two U937 subclones and HL60 were more pronounced, the latter expressing fucose residues, which might be part of the CD15 cell adhesion molecules. Some of the differences of the carbohydrate residues between the cell lines could be attributed to their differentiation within the myelomonocytic cell lineage. Lectins that bound to the cell surface were internalized via either clathrin-coated pits and vesicles or nonspecific endocytosis, indicating that functionally different classes of cell surface glycoproteins are involved in lectin binding and internalization.