Demonstration of a Normal Serum Macroglobulin Coprecipitating with the Bovine Serum Albumin (BSA)-Chicken Anti-BSA Precipitate

Summary A normal serum protein is shown to coprecipitate with the BSA-chicken anti-BSA aggregate in 1.5 M NaCl regardless of the zones of precipitin reaction and the age of the antiserum. This protein is shown to be a macroglobulin with S20,w20, and with the mobility and salting-out properties of a β- or γ-globulin. In 0.15 M NaCl, however, coprecipitation occurs with aged antiserum but not with fresh antiserum. Associated with aging is the formation of a flocculating or a gelatinous material.