Objective: To determine the fine specificity of the anti-Ro(SSA) autoimmune response in patients with systemic lupus erythematosus (SLE), and to correlate it with clinical and serological manifestations.
Methods: 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: Anti-Ro antibodies were detected in 37 (54%) patients: 33 (48%) were positive by DID, 35 (51%) by ELISA, and 25 (35%) by IB; 32 sera were reactive in at least 2 of these 3 assay systems. By IB, 12 patients had antibodies to both the 60 kDa Ro (Ro60) and the 52 kDa Ro (Ro52), 11 patients were anti-Ro60 positive, 2 patients were anti-Ro52 positive, and 12 patients were not reactive with blotted Ro antigens. However, in immunoprecipitation assays all but one anti-Ro positive sera precipitated both Ro proteins. Anti-La reactivities were found in 15 anti-Ro positive 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 positive patients (p < 0.05 vs anti-Ro negative patients), and for nephritis, for which an inverse correlation was found, since it was less frequently diagnosed in anti-Ro positive patients (p < 0.01). However, this association 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 sensitive method for detection of anti-La. Moreover, our data indicate that 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.