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 differentiated into macrophages bound to human erythrocytes oxidized with adenosine 5'-diphosphate (ADP)-Fe3+ chelate (ADP/Fe3+) in the absence of serum. The binding was prevented when the cells were treated with ADP/Fe3+ in the presence of antioxidants, indicating that oxidation of the cells is responsible for the increased susceptibility to the THP-1 cell binding. 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 membrane and lactoferrin, and their oligosaccharides, strongly inhibited the binding. On the other hand, glycoproteins with non-poly-N-acetyllactosaminyl 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 oligosaccharides and lactoferrin oligosaccharides was little affected by treatment with endo-beta-galactosidase, which specifically cleaves poly-N-acetyllactosamine to shorter oligosaccharides. Removal of the nonreducing terminal region of the saccharide chains of band 3 on the erythrocyte 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 primarily through the recognition of poly-N-acetyllactosaminyl saccharide chains of band 3, and the site of the recognition exists in the nonreducing terminal region of the saccharide chains. Clustering of band 3 molecules is proposed as a possible alteration of oxidized erythrocyte membrane which promotes the interaction of the saccharide receptor on THP-1 cells with the saccharide chains of band 3 on erythrocytes.