Accumulation of soluble fas in inflamed joints of patients with rheumatoid arthritis

OBJECTIVE: To examine the concentration of the soluble form of the Fas molecule (sFas) in the serum and synovial fluid of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). METHODS: The concentration of sFas in the serum of 15 normal subjects and in the synovial fluid and serum of 45 RA patients and 13 OA patients was determined. The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, and the level of several cytokines in serum and synovial fluid were also determined. RESULTS: The synovial fluid concentration of sFas was higher in RA than in OA patients (P < 0.005). The synovial fluid level of sFas correlated weakly with serum levels of CRP (r = 0.541), the ESR (r = 0.499), and with synovial fluid levels of interleukin-2 (IL-2) receptor (r = 0.544), IL-6 (r = -0.529), and intercellular adhesion molecule 1 (r = 0.514). Reverse transcription-polymerase chain reaction analysis revealed that synovial cells and infiltrating mononuclear cells expressed sFas messenger RNA in RA patients. CONCLUSION: Our data suggest that accumulation of sFas in the joint cavity of RA patients may inhibit apoptosis and exacerbate the inflammatory process.