Abstract： Objective To evaluate the changes of CD+4 IL-17 + T ( Th17 ) and CD+4 Foxp3 +regulatory T (Treg) cells in peripheral blood and bronchoalveolar lavage fluid (BALF),and therefore to explore the role of Th17 and Treg in cigarette smoke-induced airway inflammation/COPD in rats.Methods Forty male Wistar rats were randomly divided into 4 groups: a 12 wk smoke-exposure group,a 24 wk smokeexposure group,a 12 wk control group and a 24 wk control group (n =10 each). Cells in BALF were collected and analyzed by absolute and differential cell counts.IL-17 and IL-6 levels in serum and BALF were tested by emzyme linked immunosorbent assay (ELISA).The proportion of CD4+ IL-17 + T and CD4+Foxp3 + Treg in peripheral blood and BALF were determined by flow cytometry.The mRNA expressions of IL-17 and Foxp3 were measured by real-time PCR.Comparisons of the data between different groups were performed using one-way ANOVA,and SNK and Games-Howell test were used for comparison between 2 groups.Results Levels of IL-17 were remarkable increased in the 12 wk smoke-exposure group and the 24 wk smoke-exposure group in serum [ (52.6 ± 1.8) ng/L,(75.4 ± 6.0) ng/L] and BALF [ (78.1 ±5.8) ng/L,(95.0 ±6.8) ng/L] compared with the 12 wk control group [ (40.0 ± 3.2) ng/L,(54.5 ±4.6) ng/L] and the 24 wk control group [ (36.7 ±3.2) ng/L,(53.9 ±3.7) ng/L],all P ＜0.05.IL-6in serum was significantly increased in the 24 wk smoke-exposure group [ (31.4 ± 2.1 ) ng/L] compared with the 24 wk control group [ (11.5 ± 0.5) ng/L],and it was increased in the 12 wk and the 24 wk smoke-exposure group [ (33.3 ±2.3) ng/L,(44.6 ±3.0) ng/L] compared with the 12 wk and the 24 wk control group [ ( 15.6 ± 1.8) ng/L,( 18.0 ± 1.9) ng/L] in BALF.Ratio of Th17 was higher in the 12 wk and the 24 wk smoke-exposure groups in peripheral blood [ ( 1.81 ± 0.19 ) ％,( 3.74 ± 0.55 ) ％ ] and BALF [(7.84±0.28)％,(8.01 ±0.39)％] compared with the12 wk [(0.97 ±0.08)％,(5.64 ±0.54 ) ％ ] and the 24 wk control group [ ( 1.08 ± 0.10) ％,(5.95 ± 0.48 ) ％ ].Ratio of Treg in BALF was higher in the smoke-exposure groups [ (8.81 ± 0.49) ％,( 11.98 ± 0.72) ％ ] compared with the control groups [ (4.34 ±0.28)％,(5.21 ±0.42)％ ].The level of IL-17 mRNA was increased in the 12 wk and the 24 wk smoke-exposure group in peripheral blood (25.7 ±2.0,33.9 ± 1.5) and in BALF (22.2 ± 1.8,34.7 ±4.2) compared with the 12 wk ( 11.3 ±2.6,11.6 ±2.4) and the 24 wk ( 11.1 ±2.0,13.5 ±3.4)control groups. Foxp3 mRNA was increased in the smoke-exposure groups (24.4 ± 2.7,30.3 ± 2.7 )compared with the control groups ( 12.7 ± 2.7,14.6 ± 3.8).Th17 in smoke-exposure groups was positively correlated with counts of total cells and macrophages ( r =0.512,0.543,all P ＜ 0.05 ).Conclusions An elevated expression of Th17 and Treg cells and an increase of inflammatory cytokines were evident in airway inflammation of cigarette smoke-exposed rats,suggesting that Treg was involved in the immunological regulation and Th17 was associated with the persistent inflammation in cigarette smoke-induced airway inflammation in rats.