Coagulation, the process of clot formation, involves platelet and blood clotting factors. In humans, the coagulation mechanism is comprised of two processes, i.e. the primary hemostasis and the secondary hemostasis. The latter entails two pathways: (1) intrinsic pathway (contact activation pathway) and (2) extrinsic pathway (tissue factor pathway). Both pathways lead to the formation of fibrin.
Factor XI is a blood clotting factor that is produced from the liver. It circulates via the bloodstream as an inactive homodimer. It is involved in the intrinsic pathway of blood coagulation cascade. It is activated by factor XIIa (the activated form of factor XII) or by thrombin. Factor XII activates factor XI by cleaving arg-ala and arg-val peptide bonds. When in its activated form (i.e. factor XIa), it works with calcium ion to activate, in turn, clotting factor IX (Christmas factor). It is inhibited by proteinZ-dependent protease inhibitor.
Deficiency of factor XI results in a rare type of haemophilia, i.e. hemophilia C.
- plasma prothromboplastin antecedent
- (blood) clotting factor XI
- (blood) coagulation factor XI
- antihemophilic factor C