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 gala ctose and N-acetylgalactosamine. The carbohydrate-binding domain of mo use galactose/N-acetylgalactosamine-specific lectin was prepared in a recombinant form. The purified recombinant lectins were tested for com petitive inhibition against glycoprotein uptake and against tumoricida l effect. Thioglycolate-elicited macrophages internalized galactosylat ed bovine serum albumin in vitro. The internalization was blocked by r ecombinant macrophage lectins. Activated macrophages obtained after in traperitoneal injection of a nonspecific immune potentiator, OK432, di d not internalize galactosylated bovine serum albumin. These cells eli cited a cytotoxic effect against P815 murine mastocytoma cells, and th e 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. glycopro tein uptake and tumoricidal effector mechanisms.