The definition of the antisphospholipid syndrome (APS) is vascular thrombosis or pregnancy morbidity in persons with persistent presence in plasma of so called antiphospholipid antibodies (aPL). The syndrome can occur in absence (primary APS) or presence (secondary APS) of another systemic autoimmune disease, in particular systemic lupus erythematosus (SLE). About 25-45% of patients with SLE, the disorder in which APS was originally described, have circulating aPL.
Thrombosis in APS has been described for almost any vessel in the human body, but the most frequently involved locations for thrombosis are in the venous circulation the deep leg veins and in the arterial circulation the cerebral vessels. Pregnancy morbidity includes recurrent early pregnancy loss, fetal death after 10 weeks gestation and pre- and dysmaturity.
The relevant antibodies for APS are autoantibodies against proteins that bind anionic phospholipids, notably β2-glycoprotein 1 and prothrombin. Serologically APS is characterized by aPLs (lupus anticoagulants, anticardiolipin antibodies and anti-β2 glycoprotein 1 antibodies).
It is now generally accepted that binding of autoantibodies results in a higher affinity of β2-glycoprotein 1 for anionic phospholipids and cellular receptors. Binding of the β2- glycoprotein 1 – antibody complexes to platelets and endothelial cells results in platelet activation and tissue factor expression, respectively. Cellular activation could form the basis for the clinical manifestations of APS.
The research line on APS reflects a longstanding collaboration between the Thrombosis and Haemostasis Laboratory of the department of Clinical Chemistry and Haematolgy (Prof Dr PhG de Groot) and the department of Rheumatology & Clinical Immunology (Dr RHWM Derksen).
For more information contact Dr Ron Derksen (email: R.H.W.M.Derksen@umcutrecht.nl)