Antigenic sites related to human serum proteins in HBsAg: isolation from normal human serum of a high-molecular-weight glycoprotein reacting with antialbumin.

A novel minor constituent was isolated from normal human serum by affinity chromatography on columns of insolubilized concanavalin A and antibodies to albumin, followed by rate zonal centrifugation. This component has the following properties: a sedimentation coefficient of approximately 31; a diameter of 14--22 nm, and a buoyant density of 1.302 gm/cu cm. It contains about 1% neutral sugars and is electrophoretically heterogeneous, since two populations of particles with isoelectric points of pH 4.95 and 5.75 were separated by isoelectric focusing. It contains a single major glycopeptide with an apparent molecular weight of 72,000 daltons. Its amino acid composition is distinct from that of albumin. It elicited the formation of antibodies that also reacted with HBsAg.