Serum deoxyribonuclease I and clinical activity in systemic lupus erythematosus.

Serum deoxyribonuclease I (DNase I) activity in systemic lupus erythematosus (SLE) patients was shown to be lower than that of healthy laboratory personnel, rheumatoid arthritis, and scleroderma patients (P less than 0.001). The decrease in DNase I activity in SLE sera was not due to the effect of various autoantibodies or to heat labile DNase I inhibitor. A relationship between serum DNase I activity and active SLE was demonstrated. Patients with active lupus nephritis had the lowest levels of enzymatic activity.