Inhibition of spontaneous but not antibody-dependent cell-mediated cytotoxicity by simple sugars: evidence that endogenous lectins may mediate spontaneous cell-mediated cytotoxicity.

Using Chang and K-562 cell line cells as targets, we have observed that a number of sugars are capable of inhibiting spontaneous cell-mediated cytotoxicity (SCMC) but not antibody-dependent cell-mediated cytotoxicity (ADCC). The sugars D(-)ribose, beta-gentiobiose, N-acetyl-D-galatosamine, and alpha-lactose all significantly inhibited SCMC of Chang and K-562 cell line cells. Because these same sugars caused no inhibition of ADCC against either Chang or K-562 cell line cells in assays run simultaneously, the results do not appear to be due to a non-specific toxic effect of the sugars against the effector cells. These studies add to the evidence that ADCC and SCMC are mediated by separate receptors. Furthermore, they provide evidence that endogenous lectin receptors or lectin-like molecules may be involved in the recognition and/or effector stages leading to SCMC. Thus, NK cells may recognize targets by virtue of receptors capable of interacting with monosaccharide, disaccharide, or oligosaccharide sequences present alone, as glycolipids, and/or as glycoproteins on the target cell surface.