Antibodies to extractable nuclear antigens (ENA) in rheumatoid arthritis assayed by ELISA. A clinicopathological correlation.

A clinicopathological study of autoantibodies in the sera of 53 RA patients was performed. Antibodies to extractable nuclear antigens (ENA) were assayed by ELISA and were found in 42% of the subjects, all bound to RNAase sensitive ENA, and these antibodies were significantly associated with the presence of tendon nodules (p less than 0.05). Antibodies to dsDNA were found in 16%, and rheumatoid factor (RF) was present in 81%; neither of these antibody groups were associated with any of the clinical abnormalities examined for. Comparisons between anti-ENA, anti-dsDNA and anti-immunoglobulin autoantibody parameters in RA subjects revealed ENA and dsDNA antibody levels to be significantly mutually related (p less than 0.01) but both were independent of RF levels. We concluded that in RA, ENA antibodies constitute a unique autoantibody subset, that may result from an immune response to an autoantigen directly linked with the aetiopathogenesis of RA.