A new assay for anti-DNA antibodies in serum which includes the measurement of anti-Z-DNA.

A simple, rapid assay for measuring anti-DNA titre of serum which includes anti-Z-DNA is described. The assay involves solution binding of antibody to labelled DNA under conditions such that the DNA is altered to form a left-handed or Z-DNA structure in the presence of cobalt ions. The absence or presence of cobalt determines a B or Z form structure in DNA and antibodies to these forms are detectable. The majority of SLE and RA patients (88%) have a higher anti-DNA titre in the presence of cobalt ions. An additional 25% of SLE patients and 22/23 RA patients who had normal anti-DNA levels according to the Crithidea assay, reacted with abnormal titres in our assay. Patients experiencing a relapse in SLE also showed a large increase in anti-DNA in the presence of antigenic Z-DNA. These results suggest that monitoring anti-DNA levels in SLE and RA to detect anti-Z DNA antibodies, provides significant advantages over methods currently in use to measure anti-DNA antibodies.