Elevated levels of antibodies against oxidized low-density lipoprotein (LDL) frequently occur in patients with systemic lupus erythematosus (SLE) and these antibodies crossreact in many sera with anticardiolipin antibodies, known to be associated with thrombosis. Therefore, a study was carried out to assess the mutual relationship between antibodies against oxidized LDL and thrombosis.
The occurrence of IgG class antibodies against oxidized LDL, cardiolipin and phosphatidyl serine were determined by enzyme-linked immunosorbent assay in a series of 146 patients with SLE. Twenty-one patients had had thromboembolic complications. At least one of three tests used to detect lupus anticoagulant was positive in 34 out of 133 patients.
The level of antibodies against oxidized LDL correlated significantly with that of antibodies against cardiolipin (r = 0.52) but only marginally with antibodies against phosphatidyl serine (r = 0.18). Antibodies against cardiolipin and phosphatidyl serine, but not those against oxidized LDL, were significantly associated with the presence of lupus anticoagulant (odds ratios of the risk in the highest tertile relative to the lower tertiles of the antibody were 5.3, 6.9 and 1.1, respectively) and with thrombosis (odds ratios 2.5, 4.0 and 1.0, respectively).
The observations suggest that only those antibodies reacting specifically with cardiolipin and phosphatidyl serine are associated with thrombosis and with the presence of lupus anticoagulant in patients with SLE, whereas antibodies crossreacting with oxidized LDL and those reacting specifically with oxidized LDL are not associated.
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