Laboratoire d'hématologie, centre de transfusion sanguine, CHU d'Angers, 49033 Angers Cedex 01.
Tissue factor (TF), a transmembrane glycoprotein, is a very high affinity receptor for factor VII and activated factor VII (VIIa). Factor VII binding is rapidly followed by its activation into VIIa by various protease, including activated factor X. TF-VIIa complex formation is followed by activation of factors IX and X and thrombin generation. For this reason, TF is not normally expressed by circulating blood cells or endothelial cells. Binding of factor VII to TF expressed by extravascular cells following vascular injury is responsible for the hemostatic response. When appropriately stimulated however, monocytes and endothelial cells synthesize and express TF. This abnormal expression is believed to be responsible for thrombotic complications in a number of infectious and inflammatory diseases. Progress in our understanding of the mechanisms regulating TF expression might help in the development of more effective strategies for the treatment of diseases such as septic shock, in which TF is involved.