To investigate the effect of a new immunosuppressant, FK506, on interleukin 6 (IL-6) production by freshly prepared rheumatoid synovial cells.
Rheumatoid synovial cells were isolated from synovial tissue of patients with rheumatoid arthritis (RA) by using collagenase and DNase treatment. The surface phenotypes of the cells were analyzed by 2-color fluorescent analysis with FACScan. The levels of IL-6 in supernatant of cultured synovial cells were measured by enzyme immunoassay.
The synovial cells used were mainly composed 32 +/- 1% of HLA-DR+/LeuM3+ cells and 53 +/- 6% of HLA-DR-/LeuM3-cells. These synovial cells spontaneously produced a large amount of IL-6 in culture. This spontaneous production of IL-6 was significantly inhibited by FK506 at the concentration of 10(-8) to 10(-6) M in a dose dependent manner. In the preincubation study, FK506 required more than 12 h to inhibit IL-6 production by synovial cells.
These results suggest that FK506 may be beneficial for patients with RA via inhibiting IL-6 production in inflammatory joints.