IgM anti-β2 glycoprotein I is protective against lupus nephritis and renal damage in systemic lupus erythematosus.
OBJECTIVE
Antibodies to ß(2) glycoprotein I (IgG and IgM isotypes) have recently been added to the laboratory criteria of the revised antiphospholipid syndrome classification criteria. We investigated whether IgM anti-ß(2)-glycoprotein I (anti-ß(2)-GPI) is associated with clinical manifestations of systemic lupus erythematosus (SLE).


METHODS
Anti-ß(2)-GPI was measured in 796 patients with SLE (93% women, 53% white, 38% African American, mean age 45 yrs). IgM anti-ß(2)-GPI (> 20 phospholipid units) was found in 16%. Associations were determined with clinical manifestations of SLE and with components of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index.


RESULTS
As expected, IgM anti-ß(2)-GPI was highly associated with both the lupus anticoagulant and with anticardiolipin. It was associated with transient ischemic attack (OR 2.64, p = 0.04), but not significantly with venous or arterial thrombosis. IgM anti-ß(2)-GPI was protective against lupus nephritis (OR 0.54, p = 0.049), renal damage (p = 0.019), and hypertension (OR 0.58, p = 0.008). This protective effect remained after adjustment for ethnicity.


CONCLUSIONS
In SLE, IgM anti-ß(2)-GPI is not associated with thrombosis but is protective against lupus nephritis and renal damage. "Natural" autoantibodies of the IgM isotype may have a protective effect.
Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Taraneh
T
Mehrani
Michelle
M
Petri
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017153:Antibodies, Anticardiolipin / Q000097:blood / Q000276:immunology; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology*; D007668:Kidney / Q000473:pathology*; D016682:Lupus Coagulation Inhibitor / Q000097:blood / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000150:complications / Q000276:immunology* / Q000473:pathology*; D008181:Lupus Nephritis / Q000097:blood / Q000209:etiology / Q000276:immunology*; D008875:Middle Aged; D055815:Young Adult; D053482:beta 2-Glycoprotein I / Q000276:immunology*
D017153:Antibodies, Anticardiolipin; D007075:Immunoglobulin M; D016682:Lupus Coagulation Inhibitor; D053482:beta 2-Glycoprotein I