Originals

Rheumatology International

, Volume 13, Issue 2, pp 45-51

Interleukin-6 in synovial fluid is closely associated with chronic synovitis in rheumatoid arthritis

  • U. SackAffiliated withMax-Planck-Society, Clinical Research Unit for Rheumatology/Immunology, Institute of Clinical Immunology and Rheumatology, Department of Medicine III, University of Erlangen-Nuremberg
  • , R. W. KinneAffiliated withMax-Planck-Society, Clinical Research Unit for Rheumatology/Immunology, Institute of Clinical Immunology and Rheumatology, Department of Medicine III, University of Erlangen-Nuremberg
  • , T. MarxAffiliated withMax-Planck-Society, Clinical Research Unit for Rheumatology/Immunology, Institute of Clinical Immunology and Rheumatology, Department of Medicine III, University of Erlangen-Nuremberg
  • , P. HepptAffiliated withDepartment of Orthopedics, University of Erlangen-Nuremberg
  • , S. BenderAffiliated withInstitute of Biochemistry
  • , F. EmmrichAffiliated withMax-Planck-Society, Clinical Research Unit for Rheumatology/Immunology, Institute of Clinical Immunology and Rheumatology, Department of Medicine III, University of Erlangen-Nuremberg

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Summary

Interleukin-6 (IL-6) was detected at low levels in plasma [0.014±0.006 ng/ml (mean ± SEM] and in high amounts in synovial fluid [SF; 2.6±2.2 ng/ml (mean ± SEM)] of patients with rheumatoid arthritis. No correlation of IL-6 levels in plasma or SF with the ESR (n=15) or with histological parameters of acute local synovitis (n=10) was observed. In contrast, SF IL-6 was positively correlated with histological characteristics of chronic synovitis (n=10; P≤0.01) and elevated plasma IgG concentrations (n=15; P≤0.05). In vitro concentrations of IL-6 comparable to those detected in SF increased the production of both IgG and IgM by synovial membrane mononuclear cells. The present results contribute to the view that high local IL-6 concentrations in SF promote chronic synovitis in RA.

Key words

Interleukin-6 Synovial fluid Chronic rheumatoid arthritis Histology