FINE SPECIFICITY OF ANTI-RO(SSA) AUTOANTIBODIES AND CLINICAL MANIFESTATIONS IN PATIENTS WITH SYSTEMIC LUPUS-ERYTHEMATOSUS

Objective. To determine the fine specificity of the anti-Ro(SSA) autoi mmune response in patients with systemic lupus erythematosus (SLE), an d to correlate it with clinical and serological manifestations. Method s. The frequency of anti-Ro and anti-La autoantibodies was determined by double immunodiffusion (DID), ELISA, and immunoblotting (IB) in 69 patients with SLE and 39 controls, Protein and RNA immunoprecipitation were used to further characterize anti-Ro positive sera. Results. Ant i-Ro antibodies were detected in 37 (54%) patients: 33 (48%) were posi tive by DID, 35 (51%) by ELISA, and 25 (35%) by IB; 32 sera were react ive in at least 2 of these 3 assay systems. By IB, 12 patients had ant ibodies to both the 60 kDa Ro (Ro60) and the 52 kDa Ro (Ro52), 11 pati ents were anti-Ro60 positive, 2 patients were anti-Ro52 positive, and 12 patients were not reactive with blotted Ro antigens. However, in im munoprecipitation assays all but one anti-Ro positive sera precipitate d both Ro proteins. Anti-La reactivities were found in 15 anti-Ro posi tive patients: 13 sera were positive by IB, 11 by ELISA, and 9 by DID. Significant associations of anti-Ro antibodies with clinical symptoms were found for sicca syndrome, which was increased in anti-Ro positiv e patients (p < 0.05 vs anti-Ro negative patients), and for nephritis, for which an inverse correlation was found, since it was less frequen tly diagnosed in anti-Ro positive patients (p < 0.01). However, this a ssociation was seen only for those anti-Ro positive patients who were not reactive with Ro52 by IB. No difference was observed between anti- Ro/La and anti-Ro positive patients. Conclusion. DID and ELISA were of comparable sensitivity for detection of anti-Ro, IB was the most sens itive method for detection of anti-La. Moreover, our data indicate tha t IB may help to characterize clinically distinct subgroups of anti-Ro positive patients with SLE. Thus, determination of anti-Ro by IB may increase the prognostic value of this autoantibody.