Dual Function of Macrophage Galactose/N‐Acetylgalactosamine‐specific Lectins: Glycoprotein Uptake and Tumoricidal Cellular Recognition

We investigated whether the interaction of peritoneal macrophages with extracellular ligands is mediated by C‐type lectins specific for galactose and N‐acetylgalactosamine. The carbohydrate‐binding domain of mouse galactose/N‐acetylgalactosamine‐specific lectin was prepared in a recombinant form. The purified recombinant lectins were tested for competitive inhibition against glycoprotein uptake and against tumoricidal effect. Thioglycolate‐elicited macrophages internalized galactosylated bovine serum albumin in vitro. The internalization was blocked by recombinant macrophage lectins. Activated macrophages obtained after intraperitoneal injection of a nonspecific immune potentiator, OK432, did not internalize galactosylated bovine serum albumin. These cells elicited a cytotoxic effect against P815 murine mastocytoma cells, and the effect was blocked by recombinant macrophage lectins. These results indicated that galactose/N‐acetylgalactosamine‐specific C‐type lectins expressed on the surface of inflammatory macrophages and on activated tumoricidal macrophages mediate two distinct functions, i.e. glycoprotein uptake and tumoricidal effector mechanisms.