Synonyms for Tissue Factor include thromboplastin, CD142, and coagulation factor III. TF is an integral membrane glycoprotein associated with phospholipid and distributed in cells that synthesize it. TF is absent in all cells that are in direct contact with blood but is present in the adventitial cell layer that surrounds all blood cells, keratinocytes in the skin, and a number of epithelial cell types found in mucous membranes and many organ capsules. This distribution has been referred to as a protective “hemostatic envelope”. Atherosclerotic plaques contain TF (found in monocytes and smooth muscle cells). Exposure of TF to blood results in assembly of the cofactor TF with FVIIa. This complex is the most potent activator of the coagulation cascade and in laboratory testing is referred to as the extrinsic pathway of coagulation. The slide show entitled Coagulation Pathways (All Components) shows how TF relates to the other coagulation factors. See also the slide shows entitled Tissue Factor Pathway (Extrinsic) with Common Pathway (PT).
