A vascular endothelial surface glycoprotein present on the luminal surface of endothelial cells.
The main physiologic activator of protein C.
Thrombin generation is down regulated by thrombomodulin, a transmembrane protein situated on vascular endothelial cells, acting as the main physiologic activator of protein C.
The prothrombin time using plasma and other reagents does not contain thrombomodulin, and therefore measures thrombin generated in plasma by procoagulant drivers, but not the thrombin inhibited by anticoagulant drivers, especially protein C, which is not fully activated in the absence of thrombomodulin.