RESUMO
Objective To explore the effect of tumor necrosis factor-alpha(TNF-α) blockade therapy on circulating Th17 cell percentage and serum interleukin (IL)-17 level in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Methods Twenty-seven RA and 22 AS patients were recruited, of which 14 cases from both diseases received 40 weeks TNF blockade therapy. Twenty-four healthy blood donors were used as controls. The frequencies of circulating Th17 cells were determined by flowcytometry, and serum IL-17 level were measured by enzyme linked immunosorbent assay(ELISA). Results Significantly higher baseline circulating Th17 cells were observed in active RA and AS patients compared with the healthy controls[RA 1.03%(0.66%,1.78%) vs controls 0.50%(0.43%,0.67%), Z=-3.236, P<0.01; AS(1.16±0.09)%vs controls (0.59 ±0.061)% , t =5.226, P <0.01]. Similarly, serum IL-17 level were significantly elevated in patients with both diseases compared with controls[RA(32.3±2.5) pg/ml vs controls(14.3±2.5) pg/ml, t=5.070, P<0.01; AS 28.98(23.84,36.14) pg/ml vs controls 11.84(5.33,22.12) pg/ml, Z=-4.103, P<0.01]. After TNF-α blockade therapy, serum IL-17 was significantly decreased in both diseases groups[RA △(-13.5± 5.0) pg/ml and AS △(-16.0±1.9) pg/ml]. In contrast, no significant differences were found in the frequencies of circulating Th17 cells[RA △(0.104 5±0.212 6)% and AS △(0.002 5±0.183 8)%]. Conclusion Th17 cells and IL-17 have been implicated in the pathogenesis of RA and AS. TNF-α blockade can partially inhibit the function of Th17 cells. However, it is unable to reduce the frequencies of these cells in the circulation after 40 weeks therapy, which may explain the reasons for the relapse.