Structure and biological functions of human IgD. VII. IgD antinuclear antibodies in sera of patients with autoimmune disorders.
Indirect immunofluorescent tests were employed to study antinuclear antibodies (ANA) of the IgD class in sera from patients with autoimmune disease. In sera containing IgG-ANA, IgD-ANA was detected in 48% of patients with systemic lupus erythematosus, 37% with rheumatoid arthritis, 30% with Raynaud's disease, 23% with systemic scleroderma and 20% with discoid lupus erythematosus. Quantitative comparison of serum IgG, IgA, IgM and IgD between IgG-ANA-positive sera with and without IgD-ANA revealed that patients with IgD-ANA also had elevated serum IgA levels. The detection of IgD-ANA in over 36% of the patient population suggests that IgD may play a role in autoimmune disorders.