Sources of Tissue Factor

Abstract

Tissue factor (TF) exhibits a distinct nonuniform tissue distribution. Thus, high levels are found in highly vascularized organs such as the lung, brain, and placenta; intermediate levels in the heart, kidney, intestine, testes, and uterus; and low levels in the spleen, thymus, and liver. Several cell types are known to express TF constitutively, such as astrocytes in the brain, epithelial cells enveloping organs and body surfaces, adventitial fibroblasts and pericytes, and cardial myocytes in the heart. Smooth muscle cells in the media of the vessel wall and monocytes/macrophages contain small amounts of TF, which is enhanced substantially upon activation of the cells. Endothelial cells probably do not express TF. The popular concept of TF serving predominantly as a hemostatic envelope encapsulating the vascular bed has been challenged recently by the observation that blood of healthy individuals may form TF-induced thrombi under conditions entailing shear stress and activated platelets, corroborating the notion of blood-borne TF. Accordingly, small amounts of decrypted TF activity is detected in calcium ionophore-stimulated monocytes, and microparticles from plasma of healthy subjects possess TF-like activity subject to partial inactivation by anti-TF antibody. In addition to microparticles, plasma TF also comprises the soluble alternatively spliced human TF and truncated TF, both of which probably require factor VIIa to be physiologically active. Although it has been suggested that activated platelets possess active TF, the notion of TF as an integral platelet component is contested by more recent data. Rather, platelets may be very important in decrypting monocyte TF activity in a process entailing transfer of TF to activated platelets.

Activated Protein C Up-Regulates IL-10 and Inhibits Tissue Factor in Blood Monocytes

“…Unique among cells, monocytes not only secrete a repertoire of pro-and anti-inflammatory cytokines, but are the only blood cells known to synthesize the procoagulant molecule TF (44,45). In this study, we explored the possibility that recombinant activated protein C dampens the proinflammatory and procoagulant potential of activated monocytes by up-regulating the production of the anti-inflammatory cytokine IL-10 and by inhibiting TF activity.…”

Pravastatin prevents miscarriages in mice: role of tissue factor in placental and fetal injury

“…7,[11][12][13] A variety of inflammatory stimuli, including bacterial cell products and components of the complement system, are known to promote the expression of tissue factor (TF) on the surface of endothelial cells, monocytes, and neutrophils. [14][15][16] In view of previous studies showing that aberrant TF expression may be responsible for thrombosis, we considered the possibility that increased TF expression induces pathological activation of the coagulation pathway, placental failure, fetal death, and growth restriction in this model of spontaneous abortion.…”

Does activation of the blood coagulation cascade have a role in malaria pathogenesis?

“…TF is the clotting initiator [24][25][26] and a structural member of the cytokine receptor family, which signifies the expansion of the adaptive immune system in vertebrates, indicating a close connection of the coagulation pathways with the host response to infection 27 . Accordingly, TF has been increasingly recognized as the interface between coagulation and inflammation [27][28][29][30][31][32] .…”