Objective: TNF-α related apoptosis inducing ligand (TRAIL) is a member of TNF superfamily that promotes apoptosis by binding to the transmembrane receptors. The effects of TRAIL in patients with rhematoid arthritis (RA) are still debatable. This study was performed to evaluate the effects of TRAIL on RA by measuring serum concentration of TRAIL in patients with RA and assessing relationships between the TRAIL concentration and various clinical parameters of RA. Methods: A total of 105 patients with RA, 34 patients with osteoarthritis (OA), and 35 age- and gender-matched healthy controls were enrolled in this study. Data from the RA patients included subject's age, duration of disease, daily steroid doses, ESR, CRP, rheumatoid factor, leukocyte count, lymphocyte count, tender joint count, swollen joint count, and serum TRAIL concentration. Serum TRAIL concentration was measured by enzyme immunoassay (EIA) method. The serum concentration of TRAIL in RA patients was compared to those of OA patients and healthy controls. Relationships of TRAIL concentration with various clinical parameters were evaluated. Results: Serum concentration of TRAIL in patients with RA was significantly decreased compared to that in healthy controls (RA: 42.60⁑26.39 pg/mL, control: 57.21⁑19.49 pg/mL, p=0.029). Serum concentration of TRAIL in patients with OA (50.79⁑15.92 pg/mL) was not different from that in normal controls (p=0.115). There were no significant differences in serum TRAIL concentration between patients with RA and those with OA (p=0.360). In patients with RA, serum TRAIL concentration showed no difference between high- and normal ESR subgroups, as well as high- and normal CRP subgroups. Serum TRAIL concentration correlated significantly with ESR (r=0.406, p＜0.001). However, other clinical parameters, such as subject's age, duration of disease, daily steroid doses, CRP, leukocyte count, lymphocyte count, tender joint count, swollen joint count revealed no significant correlation with serum TRAIL concentration. Conclusion: Serum concentrations of TRAIL in RA patients were significantly lower than those in healthy controls, suggesting that apoptotic ability is decreased in the patients with RA. Serum TRAIL concentration does not seem to reflect disease activity of RA.

Keywords: Rheumatoid arthritis, TNF-α related apoptosis inducing ligand (TRAIL)