Peripheral blood and synovial fluid monocyte activation in inflammatory arthritis. II. Low levels of synovial fluid and synovial tissue interferon suggest that gamma-interferon is not the primary macrophage activating factor

Arthritis Rheum. 1987 Aug;30(8):864-71. doi: 10.1002/art.1780300804.


Because synovial fluid monocytes (SFM) in patients with inflammatory arthritis bear an activated phenotype (i.e., high expression of HLA-DR and low expression of the monocyte differentiation antigen Mo2), we assessed the role of gamma-interferon (gamma-IFN) in the activation of these cells. Sensitive and specific radioimmunoassays detected only 0.40 +/- 0.20 units/ml of gamma-IFN in the SF of patients with rheumatoid arthritis (RA) and 0.61 +/- 0.67 units/ml of gamma-IFN in the SF of patients with other forms of chronic inflammatory arthritis. There was no detectable alpha-IFN in any SF studied by radioimmunoassay. Bioassays failed to detect nonimmunoreactive IFN. Synovial tissue (ST) explants produced very little gamma-IFN (0.14 +/- 0.091 units/ml), and production was not increased by the presence of indomethacin in the cultures or by removal of adherent cells. However, gamma-IFN was produced if ST was cultivated in the presence of phytohemagglutinin. In SF and ST supernatants, gamma-IFN-mediated induction of HLA-DR on monocytes was inhibited, even though the amount of immunoreactive IFN was not affected. Prostaglandin E2 was shown to be one possible inhibitor. We demonstrated that a factor that induces HLA-DR on some individuals' peripheral blood monocytes, and cannot be neutralized by monoclonal anti-gamma-IFN antibody, is present in SF and ST supernatants. These data suggest that activation of SFM may occur by mechanisms other than gamma-IFN.

Publication types

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

MeSH terms

  • Absorption
  • Arthritis / pathology*
  • Arthritis / physiopathology
  • Blood Cells / physiology*
  • Dinoprostone
  • Humans
  • Interferon-gamma / antagonists & inhibitors
  • Interferon-gamma / metabolism
  • Interferon-gamma / pharmacology
  • Interferon-gamma / physiology*
  • Lymphocyte Activation*
  • Lymphokines / metabolism
  • Lymphokines / physiology
  • Macrophage-Activating Factors
  • Monocytes / drug effects
  • Monocytes / physiology*
  • Prostaglandins E / pharmacology
  • Synovial Fluid / cytology*
  • Synovial Fluid / metabolism
  • Synovial Membrane / metabolism


  • Lymphokines
  • Macrophage-Activating Factors
  • Prostaglandins E
  • Interferon-gamma
  • Dinoprostone