Anti-insulin antibodies and the natural autoimmune response in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by the finding of ample serum autoantibodies. The role and the origin of many of these antibodies are still obscure. The aim of this work was to study the occurrence of anti -insulin antibodies (AIA) in SLE, and to postulate, based on AIA determinat ion, on the mechanisms involved in the production of some autoantibodies in SLE. IgG and IgM AIA, anti-DNA antibodies (ADA) and anti-tetanus toroid an tibodies (ATA) were determined using ELISA in sera and B-lymphocytes cultur e media of 24 SLE patients, 10 healthy controls and 19 insulin-dependent di abetes mellitus (IDDM) patients. B- and T-lymphocytes were isolated using F icoll gradient, depleted of T-cells using cyclosporin A, EBV infected and g rown in medium. The frequencies of IgM-AIA and IgG-ADA were higher in SLE p atients than in healthy controls (P < 0.02 and P < 0.05, respectively). The rate of IgM-AIA in SLE and IDDM was comparable, while IgG-AIA was signific antly less common in SLE than in IDDM (P ( 0.05). The prevalence of ATA in SLE patients and healthy controls was similar. These findings increase the spectrum of the humoral autoimmune response in SLE and suggest that part of it (natural autoantibodies) is independent of antigen driven response.