The Cold-insoluble Globulin of Human Plasma

TLDR

CI‑globulin was purified from plasma cryoprecipitate by glycine fractionation, ethanol precipitation, and di‑ethylaminoethylcellulose chromatography. The purified protein is a homogeneous fast β‑globulin lacking fibrinogen, lipid, or coagulation factor activity, with plasma levels of ~0.33 g L⁻¹ and lower serum levels, and its removal from cryoprecipitate reduces plasma CI‑globulin by 59–79 %.

Abstract

Abstract The cold-insoluble globulin (CI-globulin) of human plasma has been highly purified. Starting with Fraction I-1, or plasma cryoprecipitate, 2.1 m glycine fractionation (15°) precipitated mainly fibrinogen; concentration of supernatant CI-globulin-enriched material (16% ethanol, -4°) was carried out prior to final purification by chromatography on di-ethylaminoethylcellulose. Chromatographically purified CI-globulin contained no detectable fibrinogen and was homogeneous upon ultracentrifugation (s20,w0 = 12.3 S); only trace amounts of NH2-terminal amino acids were detectable. CI-globulin migrated as a fast β-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 NH2-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, n = 11), 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.