[Role of phospholipids in hemostasis]

This article reviews the significance of phospholipids in the haemostatic process. The plasma membranes of activated human blood platelets provide a catalytic phospholipid surface on which the "tenase" complex (factor IXa-factor VIIIa) and the "prothrombinase" complex (factor Xa-factor Va) can be assembled. The formation of a procoagulant platelet surface involves the exposure of anionic phospholipids e.g. phosphatidylserine, and is associated with shedding of microvesicles from the membranes of activated platelets. Moreover, tissue-factor, which plays a key role in blood coagulation by initiating the extrinsic coagulation pathway, requires the presence of phospholipids for optimal biological activity. The phospholipid dependency of the coagulation system explains the prolongation of phospholipid dependent clotting tests in patients with phospholipid directed antibodies such as lupus anticoagulants.