Levels of synovial fluid interleukin-1 receptor antagonist in rheumatoid arthritis and other arthropathies. Potential contribution from synovial fluid neutrophils

Arthritis Rheum. 1993 Jun;36(6):781-9. doi: 10.1002/art.1780360607.


Objective: To measure synovial fluid (SF) levels of interleukin-1 receptor antagonist (IL-1ra) and to determine the capacity of SF neutrophils (PMN) to synthesize and release IL-1ra.

Methods: A sensitive and specific enzyme-linked immunosorbent assay was used to measure SF IL-1ra protein concentrations and IL-1ra production by isolated SF PMN:

Results: SF IL-1ra levels were elevated in 13 of 16 samples from patients with rheumatoid arthritis (RA) (mean 17.1 ng/ml), in 6 of 18 samples from patients with infectious or inflammatory, non-RA arthropathies (mean 10.6 ng/ml), and in none of 11 noninflammatory SF samples. SF IL-1ra levels correlated with SF PMN concentrations (r = 0.680, P < 0.00001). Isolated SF PMN contained preexisting IL-1ra protein in the absence of messenger RNA (mRNA). In addition, both lipopolysaccharide and granulocyte-macrophage colony-stimulating factor induced modest increases in IL-1ra mRNA by cultured SF-PMN.

Conclusion: IL-1ra levels are increased in > 80% of RA SF samples. SF PMN produce IL-1ra, possibly contributing to the levels of IL-1ra present within the SF.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Arthritis, Rheumatoid / metabolism*
  • Humans
  • Interleukin-1 / genetics
  • Interleukin-1 / metabolism
  • Joint Diseases / metabolism*
  • Neutrophils / chemistry
  • Proteins / analysis
  • Proteins / genetics
  • RNA, Messenger / analysis
  • Receptors, Interleukin-1 / antagonists & inhibitors*
  • Receptors, Interleukin-1 / genetics
  • Synovial Fluid / chemistry
  • Synovial Fluid / cytology


  • Interleukin-1
  • Proteins
  • RNA, Messenger
  • Receptors, Interleukin-1