High-molecular-weight kininogen

Prekallikrein

Biology

Hemostasis

Receptor

Biochemistry

Coagulation

Fibrinolysis

Phosphate

Immunology

Kallikrein

Tissue factor

Kininogen

Bradykinin

Inflammation

Enzyme

Internal medicine

Polyphosphate

Proinflammatory cytokine

Medicine

Factor XII

Factor IX

Blood

Combinations of proinflammatory and procoagulant reactions are the unifying principle for a variety of disorders affecting the cardiovascular system. The factor XII–driven contact system starts coagulation and inflammatory mechanisms via the intrinsic pathway of coagulation and the bradykinin-producing kallikrein-kinin system, respectively. The biochemistry of the contact system in vitro is well understood; however, its in vivo functions are just beginning to emerge. Challenging the concept of the coagulation balance, targeting factor XII or its activator polyphosphate, provides protection from thromboembolic diseases without interfering with hemostasis. This suggests that the polyphosphate/factor XII axis contributes to thrombus formation while being dispensable for hemostatic processes. In contrast to deficiency in factor XII providing safe thromboprotection, excessive FXII activity is associated with the life-threatening inflammatory disorder hereditary angioedema. The current review summarizes recent findings of the polyphosphate/factor XII–driven contact system at the intersection of procoagulant and proinflammatory disease states. Elucidating the contact system offers the exciting opportunity to develop strategies for safe interference with both thrombotic and inflammatory disorders.

Coagulation factor XII in thrombosis and inflammation