DNA-BINDING ACTIVITY OF SERUM FROM PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS

Abstract

The reaction conditions essential for reproducible use of the cellulose ester membrane filter assay for anti-DNA antibody levels in patients with systemic lupus erythematosus were described. A dependence of DNA-binding capacity on serum concentration was observed in the assay, requiring that serum concentrations be comparable in determinations of DNA-binding activity of different sera and when comparing different published studies. The DNA-binding capacity of serum from lupus patients was significantly different from that of healthy controls. The binding capacities were not significantly different between lupus patients with and without nephritis. The relative avidity of the anti-DNA antibodies were estimated from plots of 1/DNA bound vs. 1/DNA free, suggesting the avidities of the antibodies from the 2 groups of lupus patients are not significantly different. The tightness of binding between the DNA and the serum anti-DNA antibodies apparently cannot be used to predict immune complex-induced nephritis in lupus patients.