Radioimmunoassay of fragment E‐related neoantigen: validation studies and clinical application

Abstract

Measurement of fibrinogen-fibrin degradation products (FDP) levels in plasma may provide a direct index of plasmin action, and increased levels of FDP would indicate coagulopathy. We have established an E-neoantigen radioimmunoassay ( Eneo RIA) that can determine normal and pathological plasma levels of E-related FDP. The assay employs rabbit antiserum produced against fragment E derived from a plasmin digest of fibrinogen and subsequently absorbed with fibrinogen. The absorbed antiserum contains antibodies which are equally reactive with fibrinogen derived E (Fg-E) and fibrin derived E (Fb-E) but not with fibrinogen at 1 mg/ml. The Eneo RIA was validated by assay parallelism and by recovery experiments. Plasma Eneo immunoreactivities in 14 normals were 4-22 ng/ml (mean 12.7 ng/ml). Plasma Eneo levels in 23 of 24 patients with neoplastic and haematological diseases were elevated above normal (range 27-2027 ng/ml). Unusually high Eneo values were observed with three patients whose diseases were complicated by either disseminated intravascular coagulation (DIC) or deep vein thrombosis. After heparin therapy, the Eneo level of a patient with chronic DIC declined. A pathological plasma was eluted from a Sephadex G-200 column and Eneo immunoreactivity was determined on the eluates. The gel filtration pattern of Eneo indicates that E-related FDP is a family of plasmic fragments derived from crosslinked fibrin.

Progressive Exposure of E-Neoantigen Associated with Degradation of Crosslinked Fibrin by Plasmin In Vitro

“…In vivo fragment E-related protein is more likely to originate from XL-fibrin and not from fibrinogen because of the specificity of the fibrinolytic system toward fibrin. In fact, XL-fibrin degradation products were detected in patients with disseminated intravascular coagulation (21,26,27). Our recent Eneo radioimmunoassay data (28) observed in the plasma of a patient with the same disorder was consistent with the hypothesis that Eneo measured in the patient's plasma was the sum of Eneo expressed by plasmic fragments derived from XL-fibrin.…”