title: Low levels of antibodies against oxidized but not nonoxidized cardiolipin and phosphatidylserine are associated with atherosclerotic plaques in systemic lupus erythematosus.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: From the Institute of Environmental Medicine, Unit of Immunology and Chronic Disease, Karolinska Institutet, Stockholm; Department of Laboratory Medicine, Division of Clinical Physiology, and Department of Rheumatology, Karolinska Institutet at Karolinska University Hospital, Huddinge, Stockholm, Sweden.
authors.forename: Jun
authors.initials: J
authors.lastname: Su
authors.forename: Anna G
authors.initials: AG
authors.lastname: Frostegård
authors.forename: Xiang
authors.initials: X
authors.lastname: Hua
authors.forename: Thomas
authors.initials: T
authors.lastname: Gustafsson
authors.forename: Tomas
authors.initials: T
authors.lastname: Jogestrand
authors.forename: Ingiäld
authors.initials: I
authors.lastname: Hafström
authors.forename: Johan
authors.initials: J
authors.lastname: Frostegård
mesh_terms: D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D002308:Cardiolipins / Q000276:immunology*; D059168:Carotid Intima-Media Thickness; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000150:complications / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D010718:Phosphatidylserines / Q000276:immunology*; D058226:Plaque, Atherosclerotic / Q000097:blood / Q000150:complications / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D002308:Cardiolipins; D010718:Phosphatidylserines
keywords: ANTICARDIOLIPIN ANTIBODIES; ATHEROSCLEROSIS; OXIDATION; PHOSPHATIDYLSERINE; SYSTEMIC LUPUS ERYTHEMATOSUS; VULNERABLE PLAQUE