OBJECTIVE

We have reported that the prevalence of atherosclerotic plaques and their echolucency was increased in systemic lupus erythematosus (SLE). We here study antibodies against oxidized cardiolipin (anti-OxCL) and phosphatidylserine (anti-OxPS) in SLE and in relation to atherosclerosis measures.

METHODS

Patients with SLE (n = 114) were compared with age- and sex-matched population-based controls (n = 122). Common carotid intima-media thickness and plaque occurrence were determined by B-mode ultrasonography. Plaques were graded according to echogenicity as 1-4, with 1 being echolucent. Antibodies were determined by ELISA.

RESULTS

In the SLE group, the prevalence of low IgM anti-OxPS and low total IgM levels (below 33rd percentile) was increased compared to controls (p = 0.045 and p = 0.0079, respectively). Among SLE patients with atherosclerotic plaques, the prevalence of low IgM anti-OxPS (p = 0.0019) and anti-OxCL (p = 0.031) was increased. Only IgM anti-OxPS remained significant (p = 0.019) after adjusting for other significant factors. Echolucent plaques (total, or left side) were more prevalent among SLE patients with low IgM anti-OxCL and anti-OxPS when controlled for other significant factors (p < 0.05). Low total IgM was independently associated with echolucent plaque on left side (p < 0.05), but not other atherosclerosis measures. IgM anticardiolipin antibodies (aCL) and antiphosphatidylserine antibodies (anti-PS) were higher among SLE patients with cardiopulmonary disease, including arterial, valvular, and venous disease (p < 0.05). There were no associations between antibodies and other disease manifestations or activity. Both anti-OxCL and anti-OxPS, in contrast to aCL, and anti-PS, were cofactor-β2-glycoprotein I (β2-GPI)-independent.

CONCLUSION

The prevalence of low levels of IgM anti-OxCL and anti-OxPS (both cofactor-β2-GPI-independent) is associated with the presence of plaques and echolucent plaques in SLE.