Stimulation of von Willebrand factor antigen release by immunoglobulin from thrombosis prone patients with systemic lupus erythematosus and the anti-phospholipid syndrome.

The level of von Willebrand factor antigen (vWF) released by endothelial cells in response to IgG isolated from 18 patients with systemic lupus erythematosus (SLE), eight patients with the anti-phospholipid syndrome (APS) and 22 controls has been measured. Incubation with IgG from the combined patient group resulted in a significantly greater release of vWF (mean stimulation index +/- SEM, 4.57 +/- 0.78) when compared with controls (1.96 +/- 0.22, P = 0.003). Furthermore, IgG from 17 patients who had had a history of thrombosis induced higher levels of vWF release (5.33 +/- 1.09) when compared with the controls (P = 0.008). These findings suggest that IgG from patients with SLE or APS is capable of stimulating vWF release and that this ability may be implicated in the thrombotic events that are observed in these conditions.