Isolated erythroglycans have a high-affinity interaction with wheat germ agglutinin but are poorly accessible in situ.

The sugar and cell specificities of wheat germ agglutinin have been studied extensively. In particular, it is well established that wheat germ agglutinin will interact with highly sialylated glycoconjugates of the type carried by the erythrocyte glycoprotein, glycophorin (Adair, W.L. and Kornfeld, S. (1974) J. Biol. Chem. 249, 4696-4704). We have found that polylactosamines isolated from adult and fetal erythrocytes can have a high-affinity interaction with immobilized wheat germ agglutinin. In fact, this interaction is much stronger than the sialic acid-dependent interaction. Using flow microfluorimetry in conjunction with various serological and enzymatic pretreatments, we have measured the extent to which polylactosamines contribute to wheat germ agglutinin binding. We have found that most of the neuraminidase-resistant receptors on erythrocytes are polylactosamine in nature. However, this residual binding of wheat germ agglutinin to neuraminidase-treated erythrocytes is of much lower apparent affinity than the sialic acid-dependent interaction. The lower reactivity of polylactosamines at the erythrocyte surface suggests that these large glycans are actually poorly accessible.