This gene encodes coagulation factor III a cell surface glycoprotein that initiates the blood coagulation cascade by acting as a high-affinity receptor for coagulation factor VII Their complex triggers a catalytic event that activates protease cascades through limited proteolysis Unlike other coagulation cofactors which circulate as inactive precursors this factor is fully functional upon cell surface expression such as on monocytes It contains three distinct domains extracellular transmembrane and cytoplasmic Expression is induced in platelets and monocytes under procoagulatory and proinflammatory stimuli It plays a major role in HIV-associated coagulopathy and is linked to COVID-19 severity and mortality via platelet-dependent monocyte expression This protein is unique in the coagulation pathway as no congenital deficiency has been reported Alternative splicing results in multiple transcript variants encoding different isoforms