Interleukin 1 stimulation of synovial cell plasminogen activator production.

Addition of human monocyte interleukin 1 (IL-1) to cultured human synovial cells can cause an increase in both cell associated (30-fold) and extracellular (40-fold) plasminogen activator (PA) activity. This increase was inhibited by antibody directed against IL-1 and phenylglyoxal. PA activity could be detected 3 h after the addition of IL-1, continued to increase for 24 h and was dependent on RNA and protein synthesis. The molecular weight of the PA produced from the IL-1 stimulated synovial cells was 55,000 +/- 1,000. Mononuclear cell conditioned media (MCCM) also stimulated synovial cells to produce PA. This stimulation was partly inhibited by anti-IL-1 thus suggesting the presence of appreciable IL-1 activity in MCCM. These results could provide clues as to how immune events are linked to cartilage destruction associated with rheumatoid arthritis.