Depressed serum IgM levels in SLE are restricted to defined subgroups

Area of Science:

• Immunology
• Autoimmunity
• Rheumatology

Background:

• Natural IgM autoantibodies are thought to protect against autoimmune diseases.
• Systemic lupus erythematosus (SLE) is a complex autoimmune condition with diverse clinical manifestations.
• Understanding immune system variations in SLE is crucial for targeted therapies.

Purpose of the Study:

• To investigate IgM responses in a large cohort of SLE patients.
• To identify associations between specific autoantibody profiles and IgM levels.
• To explore the clinical relevance of depressed IgM in SLE.

Main Methods:

• Analysis of IgM levels in 396 SLE patients and matched controls.
• Stratification of SLE patients based on distinct autoantibody profiles (IgG anti-Ro/La, anti-cardiolipin/β2glycoprotein-I).
• Assessment of associations with genetic factors (HLA-DRB1*03) and clinical outcomes (cardiovascular disease).

Main Results:

• Depressed IgM levels were more prevalent in SLE patients compared to controls.
• SLE patients with IgG anti-Ro/La autoantibodies showed reduced natural IgM (targeting phosphorylcholine and malondialdehyde-modified protein) and total IgM.
• No significant differences in IgM levels were observed in SLE patients with anti-cardiolipin/β2glycoprotein-I autoantibodies.
• Reduced IgM levels were associated with the HLA-DRB1*03 allele in both SLE patients and controls.
• Low IgM anti-PC was linked to cardiovascular disease, particularly in SLE patients without antiphospholipid antibodies.

Conclusions:

• Depressed IgM levels in SLE are not uniform and reflect distinct immunological and genetic differences among patient subgroups.
• The association of specific autoantibodies with reduced natural IgM highlights potential mechanisms in SLE pathogenesis.
• These findings underscore the clinical significance of measuring IgM levels in SLE for understanding disease heterogeneity and potential risk stratification.