Preparation of human immunoglobulin by caprylic acid precipitation

Caprylic acid was used to precipitate nonimmunoglobulin proteins from human plasma. The crude IgG present in the supernatant (which contained 26-29% of the total protein in terms of absorbance units or 78-87% of IgG by weight) was fractionated on DEAE-cellulose, to yield pure IgG as shown by disc electrophoresis, immunoelectrophoresis and gel filtration. Pure IgG was free of plasmin and plasminogen and did not exhibit any fragmentation or aggregation during storage for periods up to 4 weeks at 40 degrees C, and its anticomplementary activity was low. Antibodies to viral agents were recovered unchanged.