Specificity of antibodies to bacterial DNA in the sera of healthy human subjects and patients with systemic lupus erythematosus.

To elucidate the epitope structure to DNA by identifying antigenic determinants on bacterial DNA bound by anti-DNA antibodies from normal human subjects (NHS) and patients with systemic lupus erythematosus (SLE). Sera from NHS and patients with SLE were tested by ELISA for the presence of antibodies to single stranded DNA from calf thymus, Micrococcus lysodeikticus, Staphylococcus epidermidis, Clostridium perfringens, and Klebsiella pneumoniae. To assess binding to conserved and nonconserved determinants, sera were absorbed on DNA-cellulose affinity columns bearing each of the bacterial DNA and then tested for binding to the other DNA antigens. Absorption of SLE sera with any of the bacterial DNA caused a loss of binding to all other bacterial DNA as well as calf thymus DNA. In contrast, absorption of NHS sera with bacterial DNA caused a loss of binding to the DNA on the affinity column with much less effect on binding to the other DNA antigens. These results indicate a marked difference in the specificity of antibodies to bacterial DNA in NHS and patients with SLE. The binding of SLE anti-DNA to predominantly conserved determinants suggests that a shift in patterns of anti-DNA specificity may be associated with the autoimmune state.