Serum DNA binding activity in healthy subjects and in rheumatic disease

Modifications of the Farr ammonium sulfate precipitation assay for DNA antibodies have increased sensitivity and led to the detection of DNA binding in the sera of healthy subjects and subjects with rheumatic disease other than systemic lupus erythematosus (SLE). The presence of binding in immunochemically pure IgG and the pattern of inhibition by native and denatured DNA support the thesis that DNA binding of normal, non‐SLE, and SLE sera is antibody and similar in kind although not in degree. The presence of antibodies to DNA in normal and non‐SLE sera may limit the qualitative role of these antibodies in SLE and render DNA antibodies similar to antiglobulin and other antinuclear antibodies in rheumatic disease.