Immunochemical Studies Of Fibrinogen Products Produced During Thrombosis

Immunochemical measurement of the products of fibrinogen proteolysis has provided a method to study the terminal events of coagulation that are initiated by thrombin as well as those events associated with the fibrinolytic actions of plasmin. Thrombin releases fibrinopeptide A (FPA) and later fibrinopeptide B (FPB). Immunologic techniques to measure FPA are now well established; determination of FPB is complicated by degradation of the peptide in plasma. Early plasmin cleavage occurs at the NH₂-terminal end of the Bβ-chain of fibrinogen yielding Bβ 1-42. This fragment exhibits limited crossreactivity with antisera to FPB. The action of plasmin at this site on fibrin I may play an important role in determining whether thrombin release of FPA ultimately leads to thrombus formation in vivo. Other early plasmin cleavage products arise from the COOH-terminal half of the α-chain. Details concerning the application of these immunochemical measurements to an understanding of the role of thrombin and plasmin-mediated proteolysis of fibrinogen and fibrin will be discussed. In addition, immunochemical attempts to detect the presence of factor XIIIa-catalyzed crosslinks will also be described.