Coagulation properties of membrane microparticles of platelets, erythrocytes, leukocytes and endothelial cells
Membrane microparticles (MPs) are formed upon cell activation and/or damage. They possess coagulation activity (accelerate blood clotting) since they contain on their surface posphatidylserine, substrate for assembling coagulation complexes, and some of them tissue factor (TF), major initiator of coagulation reactions. Circulating MPs are produced by blood cells and vessel wall endothelial cells and their amount could be changed in different pathological conditions. Comparative in vitro studies have shown that MPs derived from monocytes and endothelial cells have the highest and MPs derived from platelets, erythrocytes and granulocytes (neutrophils) much lower ability to accelerate blood plasma clotting. These differences are mainly determined by the presence of active TF in monocyte and endothelial MPs and its absence in platelet, erythrocyte and granulocyte MPs. Size variations of MPs of different cellular origin do not significantly affect their coagulation properties. Thus, coagulation (prothrombotic) blood potential could be influenced first of all by TF expressing MPs the source of which are activated and/or damaged monocytes and endothelial cells.