A study was conducted on the adhesion of Ehrlich ascites tumor cells to the surface of homologous mouse peritoneal macrophages. The tumor cells, upon treatment with concanavalin-A, a plant agglutinin, displayed a remarkable adhesion to macrophage cell surface. Tumor cell adhesion took place also when macrophages, instead of tumor cells, were pretreated with concanavalin-A. The concanavalin A-induced adhesion of tumor cells was inhibited by D-glucose or α-methyl-D-glucoside, specific inhibitors of concanavalin-A action. Similar phenomena were observed with concanavalin A-treated Sephadex granules. They adhered to macrophages, and agglutinated with themselves or with tumor cells, and these activities were inhibited by the same sugars.
These results suggest that a common mechanism might exist between tumor cell adhesion to macrophages and tumor cell agglutination induced by concanavalin-A, and this is probably due to the formation of agglutinin bridges between the two cell types.