Atherogenic antiphospholipid antibodies in antiphospholipid syndrome.

Macrophage uptake of oxidized LDL (oxLDL) plays a critical role in early stages of atherosclerosis. We previously reported that oxLDL forms stable complexes with beta2-glycoprotein I (beta2GPI), and that these complexes were frequently present in the sera of patients with systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS). oxLDL/beta2GPI complexes were shown to be antigenic targets for autoantibodies present in APS. To understand the role of autoantibodies in accelerated atherosclerosis of SLE and APS, we investigated the binding characteristics of beta2GPI and oxLDL to mouse macrophages, and the effect of anti-beta2GPI and anti-oxLDL autoantibodies on this macrophage binding. IgM anti-oxLDL antibody (derived from Apoe -/- mouse) showed inhibitory effect on oxLDL binding to macrophages. Although beta2GPI partly inhibited oxLDL binding to macrophages, IgG anti-beta2GPI autoantibody (derived from APS model mouse) showed pro-atherogenic property by promoting the binding of oxLDL/beta2GPI to macrophages.