Induction of anti-double stranded DNA antibodies in normal mice by immunization with bacterial DNA

Because of recent observations suggesting that bacterial DNA is immunogenic, the induction in normal mice of antibodies to Escherichia coli (EC) dsDNA was investigated. BALB/c and C57BL/6 mice were immunized with dsEC or ds calf thymus (CT) DNA complexed to methylated BSA in adjuvant; antibody responses were measured by ELISA. In both strains, dsEC DNA immunization induced a much higher anti-dsDNA response to dsEC DNA than did dsCT DNA immunization. Neither immunized group showed an appreciable antibody response when tested on dsCT DNA. Anti-dsDNA antibodies were also demonstrated by ELISA using synthetic DNA duplexes as well as a filter binding assay using ³H-labeled dsEC DNA as Ag. These results suggest that bacterial dsDNA is immunogenic and that at least some anti-dsDNA specificities can arise by immunization.