Fibrin is formed by the action of thrombin on fibrinogen releasing fibrinopeptides A and B from the Aα- and Bβ-chains of fibrinogen. Plasmin generated by the plasminogen activators uPA or tPA cleaves fibrin into fibrin degradation products (shown here: D-dimer, light blue, and fragment E, dark blue). Fibrin fragment E is internalized by cells and induces apoptosis of trophoblast cells. Illustration by Thomas Nardelli.