Relation of carotid plaque with natural IgM antibodies in patients with systemic lupus erythematosus

•Natural IgM-antibodies to PC may have protective properties in SLE.•Lower levels of IgM anti-PC were associated with carotid plaque in SLE.•Combining IgM anti-PC, adiponectin, and sE-selectin was better at predicting plaque.•IgM anti-PC may be a valuable biomarker for subclinical atherosclerosis in lupus.

Noninvasive carotid measurements have proven value in the estimation of future cardiovascular (CV) outcomes in systemic lupus erythematosus (SLE). Natural IgM-antibodies to phosphorylcholine (PC) epitopes can enhance apoptotic-cell clearance and induce anti-inflammatory pathways. Herein, we show that subclinical CV disease, as detected by carotid ultrasound, in a cross-sectional SLE cohort was associated with lower levels of IgM anti-PC, as well as lower levels of the ratio of IgM anti-PC/total IgM, compared to patients without plaque (p = 0.004 and p = 0.02, respectively). The IgM anti-PC/total IgM association remained significant after adjusting for age, cholesterol and hypertension. Adiponectin and sE-selectin were significantly elevated in patients with plaque, and statistical models showed that combining adiponectin, sE-selectin and IgM anti-PC/total IgM was better for predicting plaque than either test alone.These results support the hypothesis that IgM-natural autoantibodies may inhibit atherogenesis, and confirm the utility of IgM anti-PC levels as a biomarker for subclinical CV disease.