The pathogenic 16/6 idiotype in patients with silica associated systemic lupus erythematosus (SLE) and uranium miners with increased risk for development of SLE

Objective. To investigate the prevalence of the 16/6 idiotype (16/6 Id), a major cross reactive idiotype of anti-DNA antibodies involved in the pathogenesis of experimental lupus, in subjects with an exogenous risk for the development of systemic lupus erythematosus (SLE). Methods. The titer of 16/6 Id was determined by ELISA in sera of uranium miners exposed to heavy quartz dust: 15 developed definite and 12 probable SLE, 34 had clinical symptoms, and 27 had only serological signs (medium to high titer anti-dsDNA antibodies) of possible connective tissue disease (CTD) development. Results. The prevalence of 16/6 Id was higher in all groups compared to healthy blood donors. It was 18.5% in miners with SLE (definite and probable) and 22.2- 26.5% in miners with clinical and/or serological signs for developing CTD. All 16/6 Id positive miners were positive for anti-dsDNA antibodies and other autoantibodies associated with CTD. The prevalence of 16/6 Id in anti-dsDNA positive miners correlated slightly with CTD/SLE symptoms: 55.6% in patients with SLE, 47.4% in miners with possible CTD/SLE, and 22.2% in miners without CTD symptoms. Further, at short term follow-up, disease progressed in 2 miners of the 16/6 Id positive, but not in 16/6 Id negative miners. Conclusion. The detection of 16/6 Id in miners exposed to quartz dust may indicate a higher risk for development of SLE, warranting further studies of the role of 16/6 Id in the development of SLE in a cohort with the same sex, ethnicity, geographic region, and occupation.