http://repub.eur.nl/res/aut/19865/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/34785/ 2012-01-01T00:00:00Z Objective To investigate the abundance of autoantibodies to heterogeneous nuclear RNPs (hnRNPs) in systemic rheumatic diseases. Methods Recombinant human hnRNPs A1, B1, C1, E1, F, Gi, H1, I, K, and P2 were prepared. Antibodies to these antigens were determined by Western blotting and by enzyme-linked immunosorbent assay (ELISA) (for hnRNPs B1, E1, F, and H1) in serum samples obtained from patients with chronic fatigue syndrome (control subjects) and from patients with various connective tissue diseases. Results Western blotting analysis in 106 control subjects and 298 patients with a connective tissue disease revealed that antibodies to all tested hnRNP antigens, except hnRNP Gi, were significantly more prevalent in patients with Sjögren's syndrome (SS) than in control subjects. The highest reactivity was observed for hnRNPs B1, E1, F, and H1 (reactivity in >45% of patients with SS and in 2.8% of control subjects). Reactivity with hnRNPs B1, E1, F, and H1 was also evaluated by ELISA in 89 control subjects and 228 patients with a connective tissue disease. Reactivity with at least 2 of the 4 tested antigens was observed in 1.1% of control subjects, 16% of patients with systemic lupus erythematosus (SLE), and 18% of patients with SS. Reactivity with at least 3 of the 4 antigens was observed in 0% of the control subjects, 3.2% of patients with SLE, and 15% of patients with SS. Conclusion Several hnRNPs are target antigens in SS. The combined presence of antibodies to several hnRNPs was strongly associated with connective tissue disease in general and with SS in particular. http://repub.eur.nl/res/pub/23833/ 2011-03-01T00:00:00Z http://repub.eur.nl/res/pub/16529/ 2009-05-01T00:00:00Z BACKGROUND: Serum samples from patients with autoimmune connective tissue diseases that show a finely speckled antinuclear antibody (ANA) on indirect immune-fluorescence often have antibodies against unknown nuclear target antigens. To search for such autoantigens we applied a proteomic approach using sera from patients with a high ANA titer (≥640) and finely speckled fluorescence but in whom no antibodies to extractable nuclear antigens (ENA) could be identified. METHODS: Using an immunoproteomics approach we identified heterogeneous nuclear ribonucleoprotein H1 (hnRNP H1) as a novel nuclear target of autoantibody response. RESULTS: Recombinant rat hnRNP H1 reacted in Western blot analyses with 48% of 93 sera from patients with primary Sjögren syndrome and with 5.2% of 153 sera from patients with other connective tissue diseases (diseased controls). For comparison, the diagnostic sensitivity and specificity of anti-Sjögren syndrome A (SSA) antibodies for primary Sjögren syndrome in the same patient cohort were 88.2% and 76.3%, respectively. Interestingly, 5 of 11 primary Sjögren syndrome patients with no anti-SSA or anti-SSB antibodies had anti-hnRNP H1 antibodies. Anti-hnRNP H1 antibodies were preabsorbed by hnRNP H1, as demonstrated by indirect immunofluorescence. In an evaluation of the presence of anti-hnRNP H1 antibodies in 188 consecutive samples submitted to the clinical laboratory with positive ANA (titer ≥160), anti-hnRNP H1 antibodies were found in 3 of 7 (2 primary and 5 secondary) Sjögren syndrome patients and in 8.3% of the diseased controls. CONCLUSIONS: HnRNP H1 is a newly discovered autoantigen that could become an additional diagnostic marker.