Physiological and pathological role of factor XII

Introduction. The most widely accepted notion of the function of blood clotting factor XII (FXII, Hageman factor) is its involvement in the internal blood clotting pathway. However, the biological role of FXII is diverse.Aim – to review the diverse biological functions of FXII.Main findings. FXII is a serine protease. The structure of FXII has a high degree of homology with plasminogen, tissue plasminogen activator and urokinase plasminogen activator. Activated FXII (FXIIa) has five substrates: high-molecular kininogen, precallikrein, FXI, plasminogen, complement proteins (C1s, C1r). FXII provides hemostatic balance by participating in the processes of blood clotting and fibrinolysis. FXII regulates inflammatory and allergic reactions by interacting with the kallikreinkinin system and the complement system. FXII has biological activity in various cells in vivo: endotheliocytes, platelets, monocytes, neutrophils, fi broblasts, dendritic cells, which determines its diverse role in physiological and pathological processes.