DNA:anti-DNA complexes: their detection in systemic lupus erythematosus sera

Antibody to DNA was measured before and after treatment of systemic lupus erythematosus (SLE) sera with bovine pancreatic deoxyribonuclease (DNase I). In 11 of 15 cases of SLE with active renal disease there was a significant increase in DNA-binding after DNase digestion, while no such increase was noted in inactive SLE, normal controls or in patients with nonlupus renal disease. The significant rise in DNA-binding after digestion indicated that DNA had bound in vivo to the anti-DNA in these sera. A striking correlation between the occurrence of these complexes and disease activity was shown. In eight cases of SLE nephritis where serial blood samples were obtained, the greatest increase in DNA-binding after DNase digestion occurred at the time of the severest renal disease. In addition, serum from a case of SLE with acute cerebritis but without evidence of renal disease also had a significant rise in binding during the acute phase. This assay provides proof of the existence of circulating DNA:anti-DNA complexes in some cases of SLE and can also be used to measure an apparently critical parameter of disease activity.