Role of carbohydrates in rat leukemia cell‐liver macrophage cell contacts

Abstract

The mechanism by which macrophages recognize tumor cells is still unknown. Interactions were studied between rat liver macrophages and rat L-5222 leukemia cells. These tumor cells, but not normal leukocytes or erythrocytes, adhere to freshly isolated macrophages in vitro. Binding of tumor cells by macrophages can be inhibited by N-acetyl-D-galactosamine, D-galactose and more potently by glycoproteins with terminal N-acetyl-D-galactosamine or D-galactose residues. Tumor cell adhesion is Ca-dependent. The relevant leukemia cell membrane structures which bear terminal .beta.-D-galactosyl or related residues were determined as trypsin- and pronase-sensitive, and hence may presumably be glycoproteins. The tumor cell receptor on liver macrophages appears to be a lectin with the carbohydrate specificity N-acetyl-D-galactosamine > D-galactose > L-fucose.