Cell surface carbohydrate recognition and the viability of erythrocytes in circulation

The presence of sialic acid on the cell surface is crucial for the survival of mammalian erythrocytes in circulation. In contrast, sialidase-treated chicken erythrocytes retain their viability in circulation. Galactose oxidase treatment of chicken red blood cells has no effect on their viability. However, after sialidase treatment, galactose oxidase treatment results in the rapid elimination of the chicken erythrocytes from circulation. This is compatible with the interpretation that consecutive treatment with the 2 enzymes abolishes the ability of the chicken erythrocytes to regenerate the sialic acid on the cell surface. Mammalian asialo-erythrocytes are sequestered in the liver and spleen. We have shown that at the cellular level there is a preferential recognition of sialidase-treated as compared to normal erythrocytes by mononuclear spleen cells and Kupffer cells of the liver. This recognition manifests itself in both autologous and homologous systems by rosette-like adhesions. These adhesions may represent the normal physiological mechanism for the removal of senescent erythrocytes from circulation by liver and spleen since it has been previously reported that older erythrocytes contain decreased amounts of sialic acid. The mechanisms in mammals for the elimination from circulation of asialo-erythrocytes and asialo-glycoproteins, while analogous in many respects, are definitely not identical.