Changes in anti-DNA antibody affinity during exacerbations of systemic lupus erythematosus. 
The level and average functional affinity of anti-DNA antibody were measured retrospectively in successive serum samples from 5 patients with systemic lupus erythematosus.  In 2 patients, severe flares of disease activity were associated with an increase in the level and average functional affinity of anti-DNA antibodies.  Three patients who did not experience significant flares in disease activity exhibited more constant levels of antibody of lower average functional affinity.  The appearance of antibody of high functional affinity during disease exacerbations suggests that such antibodies may be pathogenic.