Isolation of Fibrinogen–Fibrin Related Antigen from Human Plasma by Immunoaffinity Chromatography: its Characterization in Normal Subjects and in Defibrinating Patients with Abruptio Placentae and Disseminated Cancer

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Abstract
Summary. Highly purified, fibrinogen–fibrin related antigen (FR-antigen) was isolated with good recovery from 1.0–2.0 ml of human plasma, by immunoaffinity chromatography with antibody specific for fibrinogen and fibrin, and plasmin degradation products X, Y, D and D-D dimer. In FR-antigen from defibrinating patients there was evidence for thrombin activity alone (mainly disseminated cancer) or both plasmin and thrombin (mainly abruptio placentae). Thus, the molar ratio of N-terminal Gly – Tyr in the FR-antigen of 18 of 20 patients strongly suggested thrombin activity (95th percentile). In addition, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) on unreduced samples frequently showed bands similar in mol wt to fragments X, Y and D, and in the reduced samples A α and Bβ chain degradation, both indicating plasmin activity. N-terminal β chain Ala was elevated in the antigen of four of 20 patients, also suggesting plasmin activity (99th percentile). Combined thrombin, plasmin and factor-XIII activity, as shown by bands in similar position to D-D and γ chain dimers, was commonly associated with high levels of serum FR-antigen (> 10 mg/dl). In some defibrinating patients, especially those with disseminated cancer, heterogeneity of unreduced FR-antigen and Aα chain degradation, both indicators of mild plasmin-like activity which are commonly seen in normals, were absent.