BINDING OF ANTI-DOUBLE STRANDED (DS) DNA-POSITIVE SERA TO DENATURED (D) DNA AND SYNTHETIC POLY[DA-DT] X POLY[DA-DT] DOUBLE-STRANDED COPOLYMER IN AN ELISA FORMAT

Using an ELISA assay anti-nuclear antibody-positive sera from 300 pati ents with various immune-related diseases and 64 anti-nuclear antibody -negative sera were analysed for binding to S1-nuclease-treated double stranded (ds) DNA. In addition, the pattern of reactivity of 50 selec ted anti-dsDNA-positive sera was established using denatured (d) DNA a nd poly[dA-dT] x poly[dA-dT] double-stranded alternating copolymer (dA T) as additional DNA antigens. None of the 64 anti-nuclear antibody-ne gative sera and 76 of the 300 anti-nuclear antibody-positive sera (25% ) were anti-dsDNA-positive. Of the anti-nuclear antibody-positive and anti-dsDNA-positive sera, 48 (63%) were from systemic lupus erythemato sus patients, and 7 (9%) from rheumatoid arthritis patients, whereas 2 1 patients (27.6%) suffered from various immune and non-immune related diseases. Anti-dsDNA-positive reactivity was highly correlated with d DNA and dAT reactivity (r = 0.906, p < 0.0001 and r = 0.93, p < 0.0001 , respectively). Although the majority of the 50 selected (37 systemic lupus erythematosus and 13 non-systemic lupus erythematosus) anti-dsD NA-positive sera concomitantly bound to both additional antigens, 7 of these (14%) did not bind to dAT, and 2 (4%) did not bind to dDNA. Ant i-dsDNA-positive sera (n = 37) showed a similar pattern, in which 8.1% and 2.7% of sera did not bind to dAT and to dDNA, respectively. In co ntrast, anti-dsDNA-negative sera from various immune-related diseases bound either ssDNA (12.5%) or dDNA and dAT (12.5%). These data suggest that dsDNA and dAT-based assays detect similar but not identical spec ificities in the sera of patients suffering from systemic lupus erythe matosus and in a proportion of non-systemic lupus erythematosus patien ts.