RECOGNITION OF POLY-N-ACETYLLACTOSAMINYL SACCHARIDE CHAINS ON IRON-OXIDIZED ERYTHROCYTES BY HUMAN MONOCYTIC LEUKEMIA-CELL LINE THP-1 DIFFERENTIATED INTO MACROPHAGES

The cells of the human monocytic leukemia cell line THP-1 differentiat ed into macrophages bound to human erythrocytes oxidized with adenosin e 5'-diphosphate (ADP)-Fe3+ chelate (ADP/Fe3+) in the absence of serum . The binding was prevented when the cells were treated with ADP/Fe3in the presence? of antioxidants, indicating that oxidation of the cel ls is responsible for the increased susceptibility to the THP-1 cell b inding. Galactose, fucose, mannose and mannan partially inhibited the binding. Glycoproteins containing poly-N-acetyllactosaminyl saccharide chains such as band 3 glycoprotein isolated from human erythrocyte me mbrane and lactoferrin. and their oligosaccharides, strongly inhibited the binding, On the other hand, glycoproteins with non-poly-N-acetyll actosaminyl saccharide chains such as glycophorin A isolated from the erythrocyte membrane fetuin and alpha(1)-acid glycoprotein, little or partially inhibited the binding. The inhibitory activity of band 3 oli gosaccharides and lactoferrin oligosaccharides was little affected by treatment with endo-beta-galactosidase, which specifically cleaves pol y-N-acetyllactosamine to shorter oligosaccharides. Removal of the nonr educing terminal region of the saccharide chains of band 3 on the eyth rocyte surface by treatment of the cells with endo-beta-galactosidase resulted in a decrease in the susceptibility of the cells to the THP-1 cell binding. These results suggest that THP-1 cells which have been differentiated into macrophages bind the oxidized erythrocytes primari ly through the recognition of poly-N-acetyllactosaminyl saccharide cha ins of band 3, and the site of the recognition exists in the nonreduci ng terminal region of the saccharide chains, Clustering of band 3 mole cules is proposed as a possible alteration of oxidized erythrocyte mem brane which promotes the interaction of the saccharide receptor on THP -1 cells with the saccharide chains of band 3 on erythrocytes.