The expression of interleukin-17(IL-17) in lung and peripheral blood of asthmatic rats and the influence of dexamethasone,and the role of IL-17 in the pathogenesis of asthma were investigated.Thirty Sprague-Dawley(SD) adult rats were randomly divided into three groups(n=10 in each group):normal group,asthmatic group,and dexamethasone-interfered group.Rat asthmatic model was established by intraperitoneal(i.p.) injection of 10% ovalbumin(OVA) and challenge with 1% OVA via inhalation.Rats in dexamethasone-interfered group were pretreated with dexamethasone(2 mg/kg,i.p.) 30 min before each challenge.The expression of IL-17 protein in serum and bronchoalveolar lavage fluid(BALF) was detected by ELISA.The expression of IL-17 mRNA in peripheral blood mononuclear cells(PBMC) and BALF cells was semi-quantitatively detected by RT-PCR.The expression of IL-17 protein in serum and BALF of asthmatic rats was significantly elevated as compared with normal rats and dexamethsone-interfered rats(P<0.01),and there was significant difference between normal rats and dexamethsone-interfered rats(P<0.05).The expression of IL-17 mRNA in PBMC and BALF cells of asthmatic rats was markedly increased as compared with normal rats and dexamethsone-interfered rats(P<0.01),and significant difference was found between normal rats and dexamethsone-interfered rats(P<0.05).It was concluded that the expression of IL-17 was increased significantly in asthmatic rats and could be inhibited partly by dexamethasone,suggesting that IL-17 might play an important role in the pathogenesis of asthma as an inflammation regulation factor. The expression of interleukin-17 (IL-17) in lung and peripheral blood of asthmatic rats and the influence of dexamethasone, and the role of IL-17 in the pathogenesis of asthma were investigated. Thirty Sprague-Dawley (SD) adult rats were randomly divided into three groups (n = 10 in each group): normal group, asthmatic group, and dexamethasone-interfered group. Rat asthmatic model was established by intraperitoneal (ip) injection of 10% ovalbumin (OVA) and challenge with 1% OVA via inhalation. Rats in dexamethasone-interfered group were pretreated with dexamethasone (2 mg / kg, ip) 30 min before each challenge.The expression of IL-17 protein in serum and bronchoalveolar lavage fluid (BALF) was detected by ELISA. expression of IL-17 mRNA in peripheral blood mononuclear cells (PBMC) and BALF cells was semi-quantitatively detected by RT-PCR. The expression of IL-17 protein in serum and BALF of asthmatic rats was significantly elevated as compared with normal rats and dexamethsone -interfered rats (P <0.01 ), and there was significant difference between normal rats and dexamethsone-interfered rats (P <0.05). The expression of IL-17 mRNA in PBMC and BALF cells of asthmatic rats was markedly increased as compared with normal rats and dexamethsone-interfered rats P <0.01), and significant difference was found between normal rats and dexamethsone-interfered rats (P <0.05). It was confirmed that the expression of IL-17 was increased significantly in asthmatic rats and could be bedeviced by dexamethasone, suggesting that IL-17 might play an important role in the pathogenesis of asthma as an inflammation regulation factor.