Partial purification and characterization of plasma DNA and its relation to disease activity in systemic lupus erythematosus.

This study reports the partial isolation and characterization of plasma DNA by phenol extraction and concentration of the extract. DNA, identified by immunologic and chemical methods, was found in plasma from both normal persons and patients with systemic lupus erythematosus in amounts varying from 0.004 to 0.4 micrograms/ml. The DNA was predominantly of low molecular weight, approximating 100 to 200 base pairs. Patients with lupus tended to have higher concentrations of plasma DNA than normal persons, with considerable overlap between the groups. Plasma DNA concentrations correlated inversely with titers of antibody to DNA but not strongly enough for prediction of either variable in individual cases. Many patients had high levels of plasma DNA and its antibody without clinical nephritis. These results indicate the ubiquity of plasma DNA and suggest the necessity of factors other than mere presence of DNA and its antibody for initiation of glomerular damage in systemic lupus erythematosus.