Cellular regulation of tissue factor.

Tissue factor is the initiator of the extrinsic coagulation pathway and is an important regulator of haemostasis. Tissue factor is constitutively expressed in numerous cells and tissues, and can be induced in monocytes and endothelial cells by different inflammatory agents. Lymphocytes and serum factors can modulate the expression of tissue factor in monocytes. The regulation of tissue factor expression in monocytes appears to be different from that in endothelial cells. Phorbol myristate acetate can inhibit as well as induce tissue factor activity in monocytes, whereas phorbol myristate acetate only induces the expression of tissue factor in endothelial cells. Tissue factor expression in monocytes from patients with infections is not always associated with DIC. The extrinsic pathway inhibitor may play a role in the development of DIC in patients with sepsis. Deposition of extravascular fibrin may be an important determinant of tissue injury.