BCG干预对哮喘小鼠调节性T细胞生成的影响

Effect of bacillus calmette-guerin treatment on airway inflammation and T regulatory cells in mice with asthma

摘要:

目的：研究表明减毒活菌卡介疫苗(BCG)能上调机体的TH1反应,从而对以TH2反应为主的哮喘等过敏性疾病起抑制作用。该文观察BCG干预后哮喘小鼠调节性T细胞生成的变化,以探讨其可能的作用机制。方法：昆明小鼠以卵白蛋白(OVA)致敏激发建立哮喘模型。于OVA致敏前及后5d分别以BCG皮内注射干预,在最后一次抗原激发后24h收集支气管肺泡灌洗液(BALF)和外周血。计数BALF中的细胞总数及嗜酸性粒细胞(EOS)的个数。并采用流式细胞仪分析外周血CD4+CD25+调节性T细胞(Treg)的百分比。开腹取脾,制备脾单细胞悬液并培养48h,收集上清液。ELISA法测定上清液中的IL-10的含量。结果：OVA致敏激发组小鼠BALF中的细胞总数为(27.27±5.36)×107/L;EOS为(6.59±1.32)×107/L较正常对照组(1.52±0.36)×107/L和0明显增高(P<0.01),而BCG干预组其BALF中的细胞总数为(13.71±3.17)×107/L及EOS的计数为(1.43±0.37)×107/L较OVA致敏激发组降低(P<0.01);哮喘组外周血CD4+CD25+Treg的百分比为(11.59±1.33)%与正常对照组(13.66±1.68)%比较明显下降(P<0.01)。而BCG干预组CD4+CD25+Treg的百分比为(14.40±2.70)%较哮喘组上升(P<0.05),同时,BCG干预组脾细胞培养上清液中IL-10的水平为7.79±1.34pg/mL,较哮喘组5.54±0.66pg/mL升高(P<0.01)。结论：BCG能明显抑制哮喘小鼠气道的炎症反应,其干预机制可能与促进调节性T细胞生成有关。

Abstract:

OBJECTIVE: Previous studies have shown that bacillus calmette-guerin (BCG) can deviate TH2 response toward TH1 response, resulting in a suppressive effect on the development of asthma/atopy. This study examined the effect of BCG treatment on regulatory T cells in asthmatic mice to investigate the possible mechanism. METHODS: Kunming mice were sensitized and challenged with ovalbumin (OVA) to establish asthmatic models. Asthmatic mice were injected intradermally with BCG five days before and after sensitization. After 24 hrs of last challenge, bronchoaveolar lavage fluid (BALF) and peripheral blood were collected .The total cells and eosinophils were counted in the BALF. The percentage of CD_4~+CD_ 25 ~+ in peripheral blood was detected with flow cytometry. Single spleen cell suspension was prepared and cultured in 1640 medium for 48 hrs and then the cytokine IL-10 level in the supernatant was determined using ELISA. The mice which were challenged with normal saline were used as the Normal control group. RESULTS: The number of total cells and eosinophils in BALF in asthmatic mice [(27.27±5.36)×10~7/L and (6.59±1.32)×10~7/L respectively] were more than in the Normal control group [(1.52±0.36)×10~7/L and zero respectively] (P<0.01). The number of total cells and eosinophils in BALF in asthmatic mice were reduced after BCG treatment [(13.71±3.17)×10~7/L and (1.43± 0.37 )× 10~7/L respectively] (P<0.01). The percentage of CD_4~+CD_ 25 ~+ in peripheral blood of asthmatic mice [( 11.59± 1.33)%] was noticeably lower than that of the Control group [(13.66±1.68)%] (P<0.01), but increased significantly in asthmatic mice after BCG treatment [(14.40±2.70)%] (P<0.05). The IL-10 level in spleen cell supernatant in the BCG-treated group (7.79±1.34 pg/mL) also increased compared with that in the untreated asthmatic mice (5.54±0.66 pg/mL) (P<0.01). CONCLUSIONS: BCG can markedly inhibit the airway inflammation in asthmatic mice possibly by promoting the production of regulatory T cells.