title: A high interleukin 1 receptor antagonist/IL-1beta ratio occurs naturally in knee osteoarthritis.
abstract: OBJECTIVE
  To assess the interleukin 1 receptor antagonist (IL-1Ra)/IL-1beta ratio in synovial fluid (SF) of patients with knee osteoarthritis (OA) or rheumatoid arthritis (RA) to determine a possible relation between cytokine level and disease activity.
  
  
  METHODS
  IL-1beta and IL-1Ra concentrations were measured by ELISA in knee SF from patients with OA (n = 42) or RA (n = 11). For OA patients, pain and disability were assessed by a visual analog scale (VAS) and the Lequesne index. RA disease activity was assessed using the Disease Activity Score 28 Joint Count (DAS28).
  
  
  RESULTS
  Patients with OA showed lower median levels of IL-1beta and IL-1Ra in SF than patients with RA (p < 0.001) but a higher IL-1Ra/IL-1beta ratio: 1793 (584-6221) versus 773.5 (187.64-1570.5) (p = 0.05). For patients with OA, the IL-1Ra/IL-1beta ratio was not associated with pain or disability. For patients with RA, the IL-1Ra/IL-1beta ratio and IL-1Ra and IL-1beta levels were related to SF white blood cell count.
  
  
  CONCLUSIONS
  High endogenous IL-1Ra/IL-1beta ratio occurs in SF from knee OA and does not correlate with pain or Lequesne index. Our results suggest that intraarticular injection of IL-1Ra might be self-limited in patients with knee OA and a naturally high SF ratio.
authors.affiliation: Université Paris 7, UFR médicale, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors.forename: Pascal
authors.initials: P
authors.lastname: Richette
authors.forename: Mathias
authors.initials: M
authors.lastname: François
authors.forename: Eric
authors.initials: E
authors.lastname: Vicaut
authors.forename: Catherine
authors.initials: C
authors.lastname: Fitting
authors.forename: Thomas
authors.initials: T
authors.lastname: Bardin
authors.forename: Maïté
authors.initials: M
authors.lastname: Corvol
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Savouret
authors.forename: François
authors.initials: F
authors.lastname: Rannou
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000276:immunology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein / Q000032:analysis*; D053583:Interleukin-1beta / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000276:immunology*; D010147:Pain Measurement; D013582:Synovial Fluid / Q000276:immunology*
chemical_list: C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D053583:Interleukin-1beta