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New antibody
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Clinical Chemistry 55: 946-954, 2009. First published March 5, 2009; 10.1373/clinchem.2008.115626
This Article
(Clinical Chemistry. 2009;55:946-954.)
? 2009 American Association for Clinical Chemistry, Inc.

Proteomics and Protein Markers

Heterogeneous Nuclear Ribonucleoprotein H1, a Novel Nuclear Autoantigen
Karolien Van den Bergh1, Herbert Hooijkaas2, Daniel Blockmans3, Ren? Westhovens4, Katrijn Op De Be?ck1, Patrick Verschueren4, Diana Dufour2, Joop P. van de Merwe5, Monika Fijak6, J?rg Klug6, Georges Michiels1, Benoit Devogelaere7, Humbert De Smedt7, Rita Derua8, Etienne Waelkens8, Norbert Blanckaert1 and Xavier Bossuyt1,a

1 Laboratory Medicine, Immunology, University Hospitals Leuven, Belgium; 2 Department of Immunology, Erasmus MC, University Medical Center Rotterdam, the Netherlands; 3 General Internal Medicine, University Hospitals Leuven, Belgium; 4 Rheumatology, University Hospitals Leuven, Belgium; 5 Department of Immunology and Department of Internal Medicine, Erasmus Medical Center Rotterdam, the Netherlands; 6 Department of Anatomy and Cell Biology, Justus-Liebig-University of Giessen, Germany; 7 Department of Molecular Cell Biology (Laboratory of Molecular and Cellular Signalling), Catholic University of Leuven, Belgium; 8 Department of Molecular Cell Biology (Laboratory of Protein Phosphorylation and Proteomics) and Biomacs, Catholic University of Leuven, Belgium.

aAddress correspondence to this author at: Laboratory Medicine, Immunology, University Hospitals Leuven, Herestraat 49, B-3000 Leuven, Belgium. Fax 00 32 16 347042; e-mail

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 Sj?gren 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?Sj?gren syndrome A (SSA) antibodies for primary Sj?gren syndrome in the same patient cohort were 88.2% and 76.3%, respectively. Interestingly, 5 of 11 primary Sj?gren 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) Sj?gren 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.

Copyright ? 2009 by the American Association for Clinical Chemistry.