Cellular interactions in tissue factor expression by blood monocytes.
Tissue factor (TF) is the cellular receptor for factor VIIa. In complex with TF, factor VIIa initiates coagulation by activation of factor IX and factor X. TF is normally not in contact with blood, but is expressed on extravascular cells which forms a haemostatic envelope ready to activate coagulation when vascular integrity is disrupted. However, under pathological conditions monocytes, but probably not endothelial cells, are stimulated to express TF activity on the surface of the cells and may thereby trigger activation of blood coagulation. For several years we have observed some individuals (high responders) with a very high response to lipopolysaccharide (LPS) as judged by induction of TF activity in their monocytes in whole blood. This phenomenon has been shown to be mediated by a P-selectin dependent interaction between granulocytes, platelets and monocytes where the release of platelet factor 4 (PF4) plays an important role. It is concluded that cellular interactions play a central role in the expression of TF activity in circulating monocytes.
Osterud
B
B
Department of Biochemistry, University of Tromsø, Norway.
D001792:Blood Platelets / Q000502:physiology*; D002448:Cell Adhesion; D006098:Granulocytes / Q000502:physiology; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000502:physiology*; D019007:P-Selectin; D010978:Platelet Factor 4 / Q000502:physiology; D010980:Platelet Membrane Glycoproteins / Q000502:physiology*; D013925:Thromboplastin / Q000378:metabolism*
D008070:Lipopolysaccharides; D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins; D010978:Platelet Factor 4; D013925:Thromboplastin