Studies on the nature of circulating DNA in systemic lupus erythematosus (SLE)

The isolation and purification of DNA from the sera of patients with SLE is described. Buoyant density determinations of this DNA using CsCl gradients suggest in some cases that it may be of endogenous origin. DNA from the synovial fluid of an SLE patient with septic arthritis was also shown to have a buoyant density of human DNA as well as being of considerable size variation. In addition, this synovial fluid contained antibody to DNA and evidence of DNA:anti-DNA complexes, suggesting that immune complexes composed of human DNA and antibody may be involved in the pathogenesis of the arthritis. Also described are preliminary experiments characterizing the conformation of the DNA present in DNA:anti-DNA immune complexes.