A comparison of wheat germ agglutinin binding between normal and sickle red blood cells

Using the label-fracture technique, an ultrastructural comparison was made of the number and distribution of wheat germ agglutinin (WGA)-binding sites between human normal and sickle red blood cells. The WGA was adsorbed to colloidal gold, and quantitative analysis of the electron micrographs revealed that more binding sites were present on the sickle erythrocytes than on the normal erythrocytes. Moreover, the sites were more clustered on the sickle red cells than on the normal red cells. Use of another lectin, Bandieraea simplicifolia-II, revealed that it did not bind to normal or sickle red cells. Because of the affinity of the WGA for sialic acid residues, it is probable that the WGA is binding to a transmembrane sialoglycoprotein, glycophorin A. The conformation and/or distribution of the glycophorin A molecules may be altered by the sickle hemoglobin that binds to the red cell membrane. Hence, as detected by WGA, new surface receptors, which could play a role in the adhesion of sickle cells to endothelium may be exposed.