OBJECTIVETo investigate the expression and procoagulant activity of phosphatidylserine (PS) on the normal peripheral blood cells of adults.

METHODSNormal peripheral blood samples were collected from 10 healthy volunteers (5 ml from each volunteer), platelets, neutrophils, lymphocytes and erythrocytes were isolated. The expression and procoagulant activity of PS on normal blood cells were identified by flow cytometry, inhibition test with lactadherin as PS probe and coagulation anticoagulant, respectively.

RESULTSThere was PS expression on a few normal blood cells (9.1%, 5.4%, 3.9% and 3.2% in platelets, neutrophils, lymphocytes and erythrocytes, respectively). The PS on these normal blood cells in vitro showed significant procoagulant activity. The plasma recalcification time was shortened by 47%, 36.5%, 25% and 12.5% by platelets, neutrophils, lymphocytes and erythrocytes, respectively; the formation of factor Xa (through both intrinsic and extrinsic pathways) and thrombin was also increased by 13% - 26% by platelets, neutrophils, lymphocytes and erythrocytes, respectively.

CONCLUSIONThe PS on normal blood cells in vivo may play a crucial role in the coagulation cascade.