Specificity and immunochemical properties of antibodies to bacterial DNA in sera of normal human subjects and patients with systemic lupus erythematosus (SLE).

To elucidate the mechanisms of anti-DNA production, we assessed the binding of sera of normal human subjects (NHS) and patients with SLE to a panel of bacterial and mammalian DNA. Using single-stranded DNA as antigens in an ELISA, NHS showed significant binding to some but not all bacterial DNA, while lacking reactivity to calf thymus DNA. Among bacterial DNA, the highest levels of binding were observed with DNA from Micrococcus lysodeikticus and Staphylococcus aureus. In contrast, SLE sera showed high levels of binding to all DNA tested. To evaluate further immunochemical properties of the anti-DNA antibodies, the subclass distribution of these responses was evaluated by subclass-specific reagents. While NHS showed a predominance of IgG2 antibodies to bacterial DNA, SLE sera had a predominance of IgG1 antibodies to these antigens. Together, these results provide further evidence for the antigenicity of bacterial DNA and suggest that NHS and SLE anti-DNA differ in the patterns of epitope recognition as well as mechanisms of induction.