Cross-reactive rheumatoid factors inrheumatoid arthritis with extra-articular disease

SUMMARY Rheumatoid factors (RF) have been shown to have considerable heterogeneity and bind with IgG aswell as with a variety of substances such as nuclear histone, non-histone nuclear protein, nitrophenylgroups or ssDNA. We describe evidence that polyclonal RF cross-reactive with ssDNA (CRRF) arewidely distributed in a variety of rheumatic diseases, and that their serum level is significantly higherin rheumatoid arthritis (RA) with extra-articular disease. Although the mechanism of the cross-reactivity is not clear, the presence of CRRF could be a serological feature of a clinical subset of RA.The high prevalence rale of CRRF in RA with extra-articular disease also suggests its pathogeneticrole in the extra-articular manifestation of this disease.