Wheat germ agglutinin affinity chromatography of human platelet membrane glycoproteins

Abstract

Wheat germ agglutinin inhibited the agglutination of paraformaldehyde-fixed washed human platelets which is induced by ristocetin in the presence of plasma von Willebrand factor, a component of the factor VIII system. Affinity columns of wheat germ agglutinin in Sepharose 4B were used to isolate the surface glycoprotein I complex from detergent solubilized human platelet membranes. Two glycoproteins of M r 150, 000 and M r 210, 000 were eluted from the wheat germ column using N-acetyl glucosamine. This mixture of isolated surface glycoproteins blocked ristocetin-induced agglutination of fixed washed platelets. F(ab′) 2 fragments of an antiserum raised to the eluted glycoprotein mixture inhibited ristocetin-induced platelet agglutination. By solid phase immunoabsorption, it was shown that the antibody which blocked the ristocetin reaction interacted with a platelet membrane protein of M r 150, 000. The results suggest that the glycoprotein I complex on the surface of the human platelet mediates von Willebrand factor dependent ristocetin-induced platelet agglutination.