Antigenic Properties Of Human Fibrin Plasmic Fragment D-Dimer And Its γ-γ Chain Remnant

Immunochemical analyses of human D-dimer and its γ-γ chain remnant were performed to identify their antigenic markers which would be of value in distinguishing between disseminated intravascular coagulation and primary fibrinogenolysis. Cross-linked fibrin was obtained by direct clotting of the fresh citrated plasma after adding excess CaCl₂. The plasmic digests of the cross-linked fibrin were fractionated by ion-exchange chromatography and gel filtration. Thus, high molecular weight D-dimer was purified. The γ-γ peptide remnant was purified by ion-exchange chromatography on CM-52 cellulose from the reduced D- dimer. Purity of both polypeptide fragments was determined by standard techniques. They were used to immunize rabbits. Antisera to D-dimer and γ-γ chain remnant were characterized in binding assays and in equilibrium competitive inhibition assays in order to analyze the expression of their antigenic determinants in intact fibrinogen and its plasmic degradation products. Antisera to D-dimer preferentially bound D-dimer and γ-γ chain remnant and to a lesser extent fragment D and fibrinogen. Similarly, antisera to γ-γ chain remnant bound mostly γ-γ , D-dimer as well as γ poiypeptide chain. There was no binding of the intact human fibrinogen. The results obtained in the competitive inhibition assays employing antisera to D-dimer and γ-γ chain remnant, before and after adsorption with fragment D or γ polypeptide chain respectively, as well as fibrin fragments are discussed in this report.