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Extended report
Elevated synovial expression of triggering receptor expressed on myeloid cells 1 in patients with septic arthritis or rheumatoid arthritis
  1. C E Collins1,2,3,
  2. D T La1,2,
  3. H-T Yang1,
  4. F Massin4,
  5. S Gibot5,
  6. G Faure4,
  7. W Stohl1,2
  1. 1
    Division of Rheumatology, Department of Medicine, University of Southern California Keck School of Medicine, Los Angeles, California, USA
  2. 2
    Los Angeles County + University of Southern California Medical Center, Los Angeles, California, USA
  3. 3
    Department of Rheumatology, Washington Hospital Center, Washington, DC, USA
  4. 4
    Laboratoire d’Immunologie, EA Relations Hôte, Environnement, Faculté de Médecine, Nancy Université, Nancy, France
  5. 5
    Réanimation Médicale, Hôpital Central, and Groupe Choc, Contrat AVENIR INSERM, Faculté de Médecine, Nancy Université, Nancy, France
  1. Correspondence to Dr W Stohl, Division of Rheumatology, University of Southern California, 2011 Zonal Avenue HMR 711, Los Angeles, CA 90033, USA; stohl{at}


Objective: To determine whether synovial expression of triggering receptor expressed on myeloid cells 1 (TREM-1) is upregulated in patients with distinct types of inflammatory or non-inflammatory arthritis.

Methods: Synovial fluid (SF) samples were analysed for levels of soluble TREM-1 (sTREM; n  =  132), tumour necrosis factor alpha (TNFα, n  =  78) and leucocyte TREM-1 messenger RNA (n  =  48). Synovial tissue from four rheumatoid arthritis (RA) patients, two patients with Crohn’s-associated arthritis, one patient with ankylosing spondylitis and one patient with osteoarthritis were examined for TREM-1 expression by immunohistology, and three of the RA samples were also analysed by Western blotting.

Results: Synovial fluid sTREM-1 levels in septic arthritis and RA were similar to each other and were each greater than those in gouty arthritis, non-septic/non-RA inflammatory arthritis and non-inflammatory arthritis. Synovial fluid TNFα and sTREM-1 levels correlated with each other, and sTREM-1 and leucocyte TREM-1 mRNA levels each correlated with SF leucocyte counts. TREM-1 in RA was expressed in situ in synovial tissue by cells of myelomonocytic lineage but was not detectably expressed in control osteoarthritis synovial tissue.

Conclusions: Synovial TREM-1 expression is increased in septic arthritis and RA. In patients with acute inflammatory arthritis, elevated SF sTREM-1 levels may point the clinician to a diagnosis of septic arthritis or RA. In RA patients, targeting TREM-1 may have therapeutic benefits by reducing local proinflammatory cytokine and chemokine release.

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  • Competing interests None.

  • Ethics approval The study protocol was approved by the Institutional Review Board of the University of Southern California Keck School of Medicine.

  • Patient consent Obtained.