Circulating autoantibodies to IgD in rheumatic diseases

Area of Science:

• Immunology
• Autoimmunity
• B cell biology

Background:

• Mature B lymphocytes express Immunoglobulin D (IgD) on their surface.
• Anti-IgD antibodies can exhibit adjuvant-like effects in experimental models.
• Autoimmune disorders are characterized by immune system dysregulation.

Purpose of the Study:

• To investigate the presence and class distribution of autoantibodies to IgD in patients with autoimmune diseases.
• To explore the potential role of these autoantibodies in disease modulation.

Main Methods:

• Utilized sensitive class-specific radioimmunoassays to detect and quantify autoantibodies to IgD in patient sera.
• Analyzed sera from patients with adult onset rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD), and juvenile RA.
• Assessed the inhibitory effects of IgD and IgG on IgA anti-IgD binding.

Main Results:

• Elevated concentrations of autoantibodies to IgD were detected in a significant percentage of RA (55%), SLE (45%), and MCTD (67%) patients, but rarely in juvenile RA (8%).
• IgA anti-IgD autoantibodies were particularly prevalent in RA and MCTD.
• IgA anti-IgD binding was specifically inhibited by IgD, suggesting antigen-specific recognition.

Conclusions:

• Autoantibodies to cell surface IgD are common in adult-onset autoimmune disorders.
• The presence of IgA anti-IgD autoantibodies may indicate a role in immune system modulation within these diseases.
• Further research is warranted to elucidate the precise mechanisms by which anti-IgD autoantibodies influence autoimmune pathogenesis.