[Thrombotic state in antiphospholipid syndrome]

The effect of plasma or IgG fraction obtained from patients with antiphospholipid syndrome (APS) on platelets, coagulation system, and also prostacyclin were examined. APS plasma or IgG fraction induced the activation of platelet aggregation, ATP release, and calcium mobilization. These effects were thought to be related to the enhancement of the direct binding of IgG fraction on platelet surface. In the study of coagulation system, although APS IgG inhibited factor X activation by the neutralization of phospholipid, a result indicating thrombotic state in APS could not be determined. APS plasma inhibited the prostacyclin synthesis in cultured endothelial cells, and the prostacyclin stability in APS plasma was reduced. These activating effect on platelets or inhibitory effect on prostacyclin of APS plasma or IgG fraction was thought to be one of the factors causing thrombotic state in APS.