PT - JOURNAL ARTICLE AU - TARANEH MEHRANI AU - MICHELLE PETRI TI - IgM Anti-ß<sub>2</sub> Glycoprotein I Is Protective Against Lupus Nephritis and Renal Damage in Systemic Lupus Erythematosus AID - 10.3899/jrheum.100650 DP - 2011 Mar 01 TA - The Journal of Rheumatology PG - 450--453 VI - 38 IP - 3 4099 - http://www.jrheum.org/content/38/3/450.short 4100 - http://www.jrheum.org/content/38/3/450.full SO - J Rheumatol2011 Mar 01; 38 AB - Objective. Antibodies to ß2 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-ß2-glycoprotein I (anti-ß2-GPI) is associated with clinical manifestations of systemic lupus erythematosus (SLE). Methods. Anti-ß2-GPI was measured in 796 patients with SLE (93% women, 53% white, 38% African American, mean age 45 yrs). IgM anti-ß2-GPI (&gt; 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-ß2-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-ß2-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. Conclusion. In SLE, IgM anti-ß2-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.