Foxp3表达与CD_4^+CD_(25)^+调节性T细胞在儿童哮喘发病中的作用

Role of Foxp3 expression and CD_4^+CD_(25)^+ regulatory T cells on the pathogenesis of childhood asthma

目的研究Foxp3基因表达与CD4+CD2+5调节性T细胞在哮喘发病中的作用。方法以确诊哮喘的患儿为研究对象,急性发作期15例、缓解期15例,同期选10例正常儿童作对照,提取外周血单个核细胞(PBMC)进行CD4、CD25表面标志及血浆、培养上清液IL-4、IFN-γ、IL-10和TGF-β等细胞因子的ELISA检测,同时收集哮喘患儿和正常儿童的诱导痰,用RT-PCR方法检测PBMC及诱导痰中转录因子Foxp3-mRNA的表达。结果PBMCCD4+CD2+5T细胞百分率在哮喘急性发作期、缓解期分别为(10·1±2·1)%、(11·7±2·5)%,低于对照组的(15·5±2·7)%(P分别<0·01、<0·05);对照组PBMC在体外培养后CD4+CD2+5细胞百分率显著升高,同培养前比较差异有统计学意义(P<0·01)。PBMCFoxp3-mRNA表达水平(Foxp3/β-actin)在哮喘急性发作期、缓解期分别为0·46±0·14、0·50±0·19,低于对照组0·77±0·22,诱导痰Foxp3-mRNA表达水平哮喘患儿也低于对照组;PBMC在体外培养后对照组Foxp3-mRNA表达水平较培养前升高(P<0·05),而哮喘患儿培养前后Foxp3-mRNA表达水平无显著变化。血浆及培养上清液IFN-γ、TGF-β在哮喘急性发作期、缓解期低于对照组(P<0·05),且IFN-γ、TGF-β与PBMCFoxp3-mRNA水平、CD4+CD2+5细胞百分率呈正相关。哮喘患儿血浆及培养上清液IL-4显著高于对照组,急性发作期血浆IL-10显著高于对照组,而缓解期与正常组无显著性差异;IL-4、IL-10与PBMCFoxp3-mRNA水平、CD4+CD2+5细胞百分率无相关性。结论哮喘患儿的TGF-β分泌不足、Foxp3基因表达降低、CD4+CD2+5调节性T细胞数量减少及分化发育障碍可能在儿童哮喘的发病中起重要作用。

Objective To explore the impact of Foxp3 expression and CD4^＋CD25^＋ regulatory T cells on pathogenesis of childhood asthma. Methods Totally 15 patients with acute asthma exacerbation, 15 children with asthma remission and 10 children who were hospitalized for skeleton deformity without atopic disorders or history of allergic diseases or respiratory infections within a month as controls were recruited in this study from Sep. 2004 to Mar. 2005. The percentage of CD4^＋CD25^＋T cells were detected by 2-color flow cytometry. The levels of interleukin （IL） -4, IL-10, interferon （IFN） -γ, transforming growth factor （TGF）-β in plasma and supematant were assayed by ELISA. Both the asthmatic children and the control children were selected to induce sputum by hypertonic saline. Sputum was processed for detecting the expression of Foxp3-mRNA. The expression of Foxp3-mRNA in both sputum and PBMC was detected by semi-quantltative RT-PCR with β-actin as internal control Results The percentage of CD4^＋CD25^＋ regulatory T cells in exacerbation and remission asthmatic children was significantly lower than that of the control children both prestimulation[（10. 1 ±2. 1） % vs. （15.5±2.7） %, （11.7±2.5） % vs. （15.5±2.7）%, P〈0.05] and poststimulation with PHA[ （ 12. 4±2. 3） % vs. （26. 9±3. 8） %, （ 17. 3±3.2）% vs. （26. 9±3. 8）%, P 〈0. 05 ]. The percentage of CD4^＋CD25^＋ regulatory T cells was significantly higher after PHA stimulation in normal children [ （ 15. 5 ± 2. 7 ） % vs. （ 26. 9± 3.8 ） % , P 〈 0. 01 ]. The expression of Foxp3-mRNA （Foxp3β-actin） in asthmatic children was significantly lower than that in the control children in both PBMC and induced sputum. The expression of Foxp3-mRNA in PBMC was significantly higher after PHA stimulation in the control children （0.77± 0.22 vs. 1.07±0.21, P〈0. 05）. However, there was no significant difference in Foxp3-mRNA expression in asthmatic children pre and post PHA stimulation. A significant positive correlation between the Foxp3-mRNA expression and the percentage of CD4^＋CD25^＋ regulatory T cells was detected. The levels of IFN-T and TGF-I~ were significantly lower in asthmatic children than those in the control children, and the levels of IFN-T and TGF-γ correlated positively with Foxp3-mRNA expression and the percentage of CD4^＋CD25^＋ regulatory T cells. The level of IL-4 both in plasma and supematant was higher in asthmatic children. The levels of IL-10 was higher only in exacerbation than in control children, the levels of IL-4 and IL-10 had no correlation with Foxp3-mRNA expression and the percentage of CD4^＋CD25^＋ regulatory T cells. Conclusion Insufficient secretion of TGF-β, decreased Foxp3 expression, insufficient number of CD4^＋CD25^＋ regulatory T cells and the defective ability of converting CD4^＋CD25^＋T cells to CD4^＋CD25^＋regulatory T cells might play an important role in pathogenesis of asthma.