Spontaneous and LPS-stimulated production of intracellular IL-1 beta by synovial macrophages in rheumatoid arthritis is inhibited by IFN-gamma.

In the peripheral blood (PB) as well as the synovial fluid (SF) of rheumatoid arthritis (RA) patients significantly elevated levels of interleukin 1 beta (IL-1 beta) were determined compared to controls by means of a sensitive and specific ELISA (median values: 280 pg/ml and 325 pg/ml vs. less than 20 pg/ml). In 12-h cell cultures of adherent cells, significantly increased spontaneous intracellular IL-1 beta production was determined in SF macrophage (SFM phi) cultures of RA patients compared to PB monocyte (PBMo) cultures of controls (median values: 91.0 ng/10(6) cells vs. 31.5 ng/10(6) cells). However, secretion must be elicited by additional stimulation with lipopolysaccharide (LPS). Interferon-gamma (IFN-gamma) significantly inhibited the spontaneous intracellular IL-1 beta production in SFM phi 12-h cultures of RA patients.