Stability of DNA/anti-DNA complexes. II. Salt lability and avidity

The kinetics of dissociation of antibody-radiolabeled dsDNA (homogeneous PM2 DNA or sonicated dsDNA of m.w. 6 x 10(5)) complexes at 37 degrees C have been examined via three independent radioimmunoassays: the Farr, Millipore Filter, and PEG assays. Two different procedures were used to study the kinetics. Either excess unlabeled DNA or high salt concentrations were employed to induce complex dissociation. Our results suggest that typical SLE sera contain at least two distinct populations of anti-dsDNA antibodies. One population is of rather high avidity and dissociates slowly in the presence of excess DNA or high salt. The other population is of considerably lower avidity and is dissociated more rapidly under these conditions. The results of a double label dissociation kinetics study provide independent evidence supporting this hypothesis.