Blood Group A Antigen in Human Erythrocytic Membranes and Membrane Fractions

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Abstract
Erythrocytic membranes from blood group A individuals were assayed for A antigen using a quantitative hemagglutination inhibition technique. The membranes were then extracted for lipid and glycoprotein. Although some A antigen was usually found in the glycoprotein fraction, most of the activity was in the lipid fraction. The sum of A antigen activity in the lipid, glycoprotein and membrane residue fractions only occasionally was equal to the A activity in the erythrocytic ghosts. When certain lipid preparations with little or no A antigen (enhancement factors) were added to the glycolipid fractions, the amount of A antigen demonstrated was usually greatly increased. Under these conditions the sum of the fractions often was much greater than the A antigen demonstrated in erythrocytic membranes. The organization or arrangement of A antigenic determinants in the red cell membranes may not always permit a stoichiometric reaction with anti-A molecules.