Depressed serum IgM levels in SLE are restricted to defined subgroups

Publication date: Available online 15 September 2017
Source:Clinical Immunology
Author(s): Caroline Grönwall, Uta Hardt, Johanna T. Gustafsson, Kerstin Elvin, Kerstin Jensen-Urstad, Marika Kvarnström, Giorgia Grosso, Johan Rönnelid, Leonid Padykov, Iva Gunnarsson, Gregg J. Silverman, Elisabet Svenungsson
Natural IgM autoantibodies have been proposed to convey protection from autoimmune pathogenesis. Herein, we investigated the IgM responses in 396 systemic lupus erythematosus (SLE) patients, divided into subgroups based on distinct autoantibody profiles. Depressed IgM levels were more common in SLE than in matched population controls. Strikingly, an autoreactivity profile defined by IgG anti-Ro/La was associated with reduced levels of specific natural IgM anti-phosphorylcholine (PC) antigens and anti-malondialdehyde (MDA) modified-protein, as well total IgM, while no differences were detected in SLE patients with an autoreactivity profile defined by anti-cardiolipin/β2glycoprotein-I. We also observed an association of reduced IgM levels with the HLA-DRB1*03 allelic variant among SLE patients and controls. Associations of low IgM anti-PC with cardiovascular disease were primarily found in patients without antiphospholipid antibodies. These studies further highlight the clinical relevance of depressed IgM, and suggest that low IgM levels in a SLE patient may reflect underlying immunological differences.



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