Influence of assay conditions on ELISA determinations of anti-DNA antibodies.

The influence of assay conditions on anti-DNA determinations by an enzyme-linked immunosorbent assay (ELISA) was investigated to evaluate the detection of various DNA antigenic specificities. Among 4 monoclonal anti-DNA antibodies of MRL-lpr/lpr strain origin, 2 showed higher titers in 100 mM NaCl-50 mM Tris, pH 7.5 (Tris-NaCl) than in phosphate-buffered saline (PBS). The determination of 'polyspecificity' for these monoclonal products also depended on the set of conditions used for assay with inhibitory activity of polynucleotides differing in the 2 buffers. The buffer effects were not confined to the monoclonal antibodies as increases in anti-DNA titers were demonstrated for certain SLE patient sera when assayed in Tris-NaCl rather than PBS; sera of MRL-lpr/lpr mice showed an opposite effect, however, with enhancement of anti-DNA activity by PBS. These results suggest that the representation of antigenic sites on DNA may be variably affected by the conditions of assay, altering quantitative and qualitative assessment of this important serological marker.