Effects of anti‐β2GPI antibodies on VWF release from human umbilical vein endothelial cells and ADAMTS13 activity

Abstract

Unlabelled Box BackgroundAntiphospholipid syndrome (APS) is characterized by recurrent thromboembolic events in the setting of pathologic autoantibodies, some of which are directed to β2‐Glycoprotein 1 (β2GPI). The mechanisms of thrombosis in APS appear to be multifactorial and likely include a component of endothelial activation. Among other things, activated endothelium secretes von Willebrand factor, a hemostatic protein that in excess can increase the risk of thrombosis. ObjectiveWe hypothesized that anti‐β2GPI antibodies could regulate the release and modulation of VWF from endothelial cells. Patients/MethodsIsolated anti‐β2GPI antibodies from patients with APS were assayed for their ability to induced VWF release from HUVECs and modulate the effects of ADAMTS13 in a shear‐dependent assay. ResultsWe observed that anti‐β2GPI antibodies from some patients with APS induced VWF release from human endothelial cells but did not induce formation of cell‐anchored VWF‐platelet strings. Finally, we also determined that one of the Anti‐β2GPI antibodies tested can inhibit the function of ADAMTS13, the main modulator of extracellular VWF. ConclusionsThese results suggest that VWF and ADAMTS13 may play a role in the prothrombotic phenotype of APS.