Histological features of rheumatoid arthritis patients having antibodies to enterobacterial common antigens: correlation of antibody levels with semiquantitative histologic scores and laboratory markers.

OBJECTIVE To ascertain whether clinically diagnosed rheumatoid arthritis (RA) patients having antibodies to enterobacterial common antigens (ECA) in synovial fluid (SF) have a histological appearance characteristic of RA synovitis. METHODS Twenty-five RA patients for which synovial biopsy specimens were preserved, were selected from 58 patients with RA tested for antibodies to ECA in SF The synovial tissue specimens were examined histologically using a semiquantitative scoring system with quantitative counts. The correlation of anti-ECA antibody levels with total scores for synovitis and laboratory markers in three RA patient groups (markedly positive, moderately to slightly positive, and negative according to anti-ECA antibody levels) was analyzed statistically. RESULTS Histologic examination in the markedly positive RA group (total score for synovitis, range 18-20 points) revealed typical histological features of rheumatoid synovitis. Total scores for synovitis were significantly higher in both the markedly positive and moderately to slightly positive RA groups than in the negative RA group. A comparison of anti-ECA antibody levels with total scores for synovitis revealed a strong and significant correlation. Furthermore, levels of anti-ECA antibodies were also correlated with rheumatoid factor and C-reactive protein. CONCLUSION Clinically diagnosed RA patients having anti-ECA antibodies in SF showed typical or characteristic histological features of RA synovitis. Our data suggest that a group of RA patients with an entrobacterial etiology exists in larger groups of patients with RA which is thought to be a heterogeneous disease.