Interleukin-6 in synovial fluid and serum of patients with rheumatoid arthritis and other inflammatory arthritides

Authors

  • Frédéric A. Houssiau MD,

    Research Assistant, Corresponding author
    1. Experimental Medicine Unit, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology; the Rheumatology Unit, Department of Internal Medicine, Cliniques Universitaires Saint-Luc; the Rega Institute, Katholieke Universiteit Leuven; and the Ludwig Institute for Cancer Research, Brussels, Belgium
    • Université Catholique de Louvain 5390, Avenue E. Mounier, Brussels, B-1200, Belgium
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  • Jean-Pierre Devogelaer MD,

    Associate Head
    1. Experimental Medicine Unit, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology; the Rheumatology Unit, Department of Internal Medicine, Cliniques Universitaires Saint-Luc; the Rega Institute, Katholieke Universiteit Leuven; and the Ludwig Institute for Cancer Research, Brussels, Belgium
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  • Jo Van Damme PhD,

    Research Associate
    1. Experimental Medicine Unit, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology; the Rheumatology Unit, Department of Internal Medicine, Cliniques Universitaires Saint-Luc; the Rega Institute, Katholieke Universiteit Leuven; and the Ludwig Institute for Cancer Research, Brussels, Belgium
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  • Charles Nagant De Deuxchaisnes MD,

    Professor of Rheumatology
    1. Experimental Medicine Unit, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology; the Rheumatology Unit, Department of Internal Medicine, Cliniques Universitaires Saint-Luc; the Rega Institute, Katholieke Universiteit Leuven; and the Ludwig Institute for Cancer Research, Brussels, Belgium
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  • Jacques Van Snick MD

    Head of Immunology Group
    1. Experimental Medicine Unit, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology; the Rheumatology Unit, Department of Internal Medicine, Cliniques Universitaires Saint-Luc; the Rega Institute, Katholieke Universiteit Leuven; and the Ludwig Institute for Cancer Research, Brussels, Belgium
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Abstract

Interleukin-6 (IL-6), also called 26-kd protein, hybridoma plasmacytoma growth factor, β2-interferon, or B cell stimulatory factor 2, is a recently described human cytokine with multiple growth and differentiation activities. Using a very sensitive bioassay based on the growth factor activity of this protein for B cell hybridomas, we found that IL-6 activity was significantly elevated in synovial fluid from patients with rheumatoid arthritis (RA) or other inflammatory arthritides, as compared with that in a group of patients with osteoarthritis. Moreover, IL-6 was detected in about one-third of the serum samples from patients with RA. In the latter group, we found a significant correlation between serum IL-6 activity and serum levels of C-reactive protein, α1-acid glycoprotein, α1-antitrypsin, fibrinogen, and haptoglobin, which indicates that IL-6 is related to disease activity in patients with RA.

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