Effect of purified anti–β2-GP1 autoantibodies on thrombus size. Autoantibodies reactive with anti–β2-GP1 were isolated from the purified IgG of patient serum. Anti–β2-GP1-depleted IgG is the IgG from a patient that does not bind to the β2-GP1-agarose column. (A) Anti–β2-GP1 autoantibodies from patient A (10 μg), anti–β2-GP1-depleted IgG from patient A (1 mg), and control normal serum IgG (1 mg) were infused into wild-type mice 5 minutes before laser-induced arteriolar wall injury in addition to Fab fragments of rat monoclonal anti–mouse CD41 antibody conjugated to Alexa 647. Representative images of the fluorescence signal associated with platelets (red) over 180 seconds after vessel injury are shown within the context of the bright-field histology. (B) The median integrated platelet fluorescence (F Platelet) associated with platelet thrombus formation in 3 mice after infusion of anti–β2-GP1 autoantibody (n = 25 thrombi), 3 mice after infusion of IgG depleted of anti–β2-GP1 autoantibodies (n = 36 thrombi), and 4 mice after infusion of control IgG (n = 34 thrombi) is presented over 250 seconds after vessel wall injury. Light gray represents anti–β2-GP1 autoantibodies; gray; IgG-depleted of anti–β2-GP1 autoantibodies; and black, control IgG.
