Autoantibodies against oxidized low-density lipoprotein in antiphospholipid syndrome

The prevalence and clinical significance of anti-oxidized low-density lipoprotein antibodies (anti-ox-LDL) were evaluated in patients with the antiphospholipid syndrome (APS). Anti-ox-LDL were measured in the sera of 107 patients with APS (64 primary APS, 43 secondary to systemic lupus erythematosus) by enzyme-linked immunosorbent assay (ELISA) utilizing malondialdehyde (MDA)-modified LDL as antigen. In the same patients, anticardiolipin antibodies (aCL) and anti-beta 2-glycoprotein I antibodies (anti-beta 2GPI) were also measured. A positive titre of anti-ox-LDL was detected in 22% of patients, but only in 6% of control subjects (chi(2) = 12, P = 0.0005). Levels of anti-ox-LDL were higher in patients with arterial thrombosis (n = 58) than in those without (n = 49) (P = 0.0001). Anti-ox-LDL levels correlated weakly with those of aCL (r = 0.196, P = 0.043), but not with those of anti-beta 2GPI (r = 0.076). Our findings suggest that elevated levels of anti-sx-LDL may represent another potential marker of APS, particularly of patients prone to arterial thrombosis.