Immunochemical studies of infectious mononucleosis. IX. Heterophile antigen associated with a glycoprotein from the bovine erythrocyte membrane.

A glycoprotein was isolated from the membrane of the bovine erythrocyte by refluxing the acetone- and ethanol-extracted stroma residue with 75% ethanol. The glycoprotein was purified by phosphocellulose chromatography, ethanol precipitation, lipidsolvent extraction and DEAE chromatography. The glycoprotein appeared to have two serological determinants, both reactive with antibodies present in the sera of patients with infectious mononucleosis. One of the determinants is similar to the Paul-Bunnell heterophile antigen found on sheep erythrocytes. It is dependent on carbohydrate, including sialic acid residues. Another specificity, seemingly not shared by sheep erythrocytes to any great extent, is resistance to neuraminidase and to alkaline borohydride treatment and thus it may be located either on the polypeptide portion of the molecule or on an alkali-stable oligosaccharide. The purified glycoprotein comprises 73% amino acids. Carbohydrate components and their molar ratios were sialic acid (1.0): galactose (1.5): N-acetylglucosamine (1.1): N-acetylgalactosamine (0.5): mannose (0.1).