Elevations in synovial fluid plasminogen activator in patients with rheumatoid arthritis.

Plasminogen activator (PA) activity in synovial fluid (SF) obtained from patients with rheumatoid arthritis (RA) is elevated when compared to SF obtained from patients with osteoarthritis (OA). Immunological studies and lack of evidence for a decrease in PA inhibitors, or an increase in PA stimulators, suggest that elevations in RA SF PA activity reflect increases in PA level. Although the origin(s) of SF PA was not identified, the enzyme resembles urokinase and RA synovium may be a contributing source. These observations are consistent with a possible active role of PA in the pathogenesis of RA.