Fibrin is degraded by -

Clotting also sets into motion a fibrinolytic cascade that moderates the ultimate size of the clot. Fibrinolysis is largely carried out by plasmin, which breaks down fibrin and interferes with its polymerization. The resulting fibrin split products (FSPs or fibrin degradation products) also can act as weak anticoagulants. Elevated levels of FSPs (most notably fibrin-derived D-dimers) can be used for diagnosing abnormal thrombotic states including disseminated intravascular coagulation (DIC), deep venous thrombosis, or pulmonary thromboembolism. Plasmin is generated by proteolysis of plasminogen, an inactive plasma precursor, either by factor XII or by plasminogen activators. The most impoant of the plasminogen activators is tissue-type plasminogen activator (t-PA); t-PA is synthesized principally by endothelial cells and is most active when attached to fibrin. ( Robbins Basic Pathology, 9 th edition, page 85)