The cold-insoluble globulin of human plasma. I. Purification, primary characterization, and relationship to fibrinogen and other cold-insoluble fraction components.

The cold-insoluble globulin (CI-globulin) of human plasma has been highly purified. Starting with Fraction I-l, or plasma CryOpreCipitate, 2.1 M glyCine fractionation (15O) precipitated mainly fibrinogen; concentration of supernatant CI-globulin-enriched material (16% ethanol, -4’) was carried out prior to final purification by chromatography on diethylaminoethylcellulose. Chromatographically purified CIglobulin contained no detectable fibrinogen and was homogeneous upon ultracentrifugation (s&J,~ = 12.3 S); only trace amounts of NHs-terminal amino acids were detectable. CIglobulin migrated as a fast P-globulin in agarose gel or cellulose acetate strip electrophoresis. In immunoelectrophoretic experiments, CI-globulin formed a single precipitin arc against an anti-CI-globulin serum. There was no detectable lipid, fibrin-stabilizing factor (Factor XIII), anti-hemophilic Factor B (Factor IX), plasminogen, plasmin, or thrombin inhibitory activity; low levels of anti-hemophilic factor A (Factor VIII) activity were present. There was no evidence of any alteration of the electrophoretic, ultracentrifugal, or NH,terminal characteristics of CI-globulin following thrombin treatment or heating to 56” for 5 min. The plasma CI-globulin level, estimated by antigen-antibody crossed electrophoresis, was 0.33 g per liter (range = 0.26 to 0.38, n = 12). The level in serum, 0.20 g per liter (range = 0.14 to 0.30, 12 = ll), was consistently lower (19 to 52 %), presumably attributable to CI-globulin incorporation or occlusion in the fibrin clot. After removal of plasma cryoprecipitate and Cohn Fraction I, supernatant CI-globulin levels were reduced by 59 and 79%, respectively.