Factor XII

**Factor XII**, also known as contact, recombinant or Hageman factor, is one of the key coagulation factors and plays an important role in the regulation of hemostasis.

**Factor XII** is a glycoprotein that is synthesized in the liver and vascular endothelial cells. It is synthesized and stored as two components, the first component is stored in an activated form, and the second component (C1r and C1s) is inactive and does not require activation to act. These two components combine to form the complete factor XII. When in an inactive form, factor XII can be activated by the plasminogen activation cascade, which includes cintic acid, thrombin and factor XI. Activation of factor XII leads to its transformation into the contact phase/Hageman factor/factor XIIa. This process is regulated by phosphorylation of the Y143 tyrosine site on protein C by activating the complement regulatory mechanism known as the leukocyte activation cascade. Activated factor XII then binds factor XIII at the plasma membrane and initiates a cascade of sequential coagulation reactions, including the formation of bradykinin and stimulation of fibrin polymerization and collagen contraction. This promotes the formation and strengthening of a blood clot on damaged tissue (for example, due to vascular injury or bleeding).

Over time, the results of many studies have led to the fact that the importance of this factor for the development of human health and well-being has become obvious. Factor XIIi has been found to be a key factor in the development of many diseases associated with disaggregation, such as cardiovascular diseases, thrombosis and microcirculatory disorders in patients with HIV and other blood coagulation disorders. With insufficient production of factor XIii, there is an increased tendency to bleeding and resistance to the formation of blood clots, and with its excessive formation, the risk of thrombus formation in the arteries (venous thrombi) increases. In a study of patients with atherosclerosis, high levels of factor XII were found to be associated with an increased risk of cardiovascular disease and myocardial infarction. This mechanism reflects the need for additional regulation of factor XIII in clinical practice when treating patients with bleeding disorders. Patients with insufficient amounts of this protein usually require additional treatment to increase factor Xii levels (which helps reduce bleeding) or to inhibit further clotting (eg, low molecular weight heparin or other anticoagulants), while patients with excess factor Xii require supportive care. therapy and the use of antifibrinolytic agents, as they may worsen side effects such as open ulcers. It is important to remember that bleeding disorders are not an independent pathology, but rather indicate underlying diseases of the body.

Factor XII (also known as contact factor or Hageman factor) is one of the blood clotting factors that plays an important role in the regulation of hemostasis. This factor is involved in the formation of blood clots at the site of vascular damage and prevents excessive bleeding.

Factor XII is a glycoprotein that consists of two polypeptide chains linked by covalent bonds. One chain contains several domains that are involved in the binding of the factor to the cell surface, and the other chain contains domains that are involved in the activation of the factor.

When factor XII binds to the surface of cells (such as endothelial cells), it is activated, resulting in the formation of a complex with other proteins such as factor XIII and factor XI, which are also involved in blood clotting. Factor XII is activated by a variety of stimuli, including vascular injury, inflammation, and bacterial infections.

A lack of factor XII can lead to blood clotting problems and an increased risk of bleeding. On the other hand, excess factor XII can also be harmful, as it can lead to the formation of blood clots in blood vessels and poor circulation.

Although factor XII plays an important role in blood clotting, it may also be involved in other processes such as the immune response and inflammation. For example, factor XII can promote complement activation, which is part of the immune system.

In general, factor XII is an important blood clotting factor, and its imbalance can lead to various diseases associated with hemostasis disorders, such as thrombosis or bleeding.