| Background As one of the most common chronic diseases during childhood, the prevalence of asthma has been increasing in past decades. How to control and prevent asthma becomes a key issue all over the world. Previous studies have proved that asthma is a chronic airway inflammation mediated by Th2 cells predominance and other cells including eosinophil, mast cell, neutrophil and airway epithelial cell. But the imbalance of Th1 and Th2 could not explain all changes of asthma. The impact of regulatory T cells (Tr), which are characterized by their ability to suppress effector T cells of either Th1 or Th2 mediated inflammation, on the pathogenesis of asthma has not been clarified. So far which cells play the critical role on airway inflammation of childhood asthma has not been exactly identified. In chapter one, we investigated the impact of Foxp3 gene expression and CD4+CD25+ regulatory T cells on the pathogenesis of children with asthma. In chapter two, we compared the cell classification, levels of IL-8, IL-9 and eotaxin and their correlation from induced sputum between asthmatic children and normal controls. Objective 1. To investigate the percentage of CD4+CD25+ regulatory T cells and Foxp3-mRNA expression in PBMC of children with asthma pre and post PHA stimulation in comparison with normal controls. 2. To detect the levels of IL-4, IL-10, IFN-γ, TGF-β from plasma and supernatant stimulated by PHA of children with asthma and normal controls; 3. To determine the correlation between Foxp3-mRNA expression, the percentage of CD4+CD25+ regulatory T cells and cytokines level; 4. To explore cell classification and the levels of IL-8, IL-9, eotaxin in induced sputum of asthmatic children in comparison with normal controls. Methods 1. Totally 10 patients with acute asthma exacerbation, 10 children with asthma remission and 8 normal controls were recruited in this study. 2. 2-color of flow cytometry was used for detection of the percentage of CD4+CD25+ T cells. 3 .The levels of IL-4, IL-10, IFN-γ, TGF-β from plasma and supernatant, IL-8, IL-9 and eotaxin of sputum supernatant were detected by ELISA. 4 .The expression of Foxp3-mRNA was detected by semi-quantities RT-PCR with β-actin as internal control. 5 .Correlation between levels of Foxp3-mRNA and cytokines, percentage of CD4+CD25+ regulatory T cells and cytokines, IL-8, IL-9 and neutrophil was done by SPSS11.0. Results 1 .The percentage of CD4+CD25+ regulatory T cells in asthmatic children was significantly lower than that in normal children pre( 10.1±2.1% vs 15.5±2.6%, 11.7±2.6% vs 15.5±2.6%, p<0.05) and post(12.4±2.3% vs 26.9±3.5%, 17.3±3.2% vs 26.9±3.5%, p<0.05) PHA stimulation. 2 .The expression of Foxp3-mRNA in asthmatic children was significantly lower than that in normal children whatever in PBMC or sputum. 3 . The levels of IL-4 and IL-10 both in plasma and supernatant were significantly higher in asthmatic children, but the levels of IFN-γ and TGF-β were significantly lower in asthmatic children than that in normalchildren. 4 .A significant positive correlation between the Foxp3-mRNA expression and the percentage of CD4+CD25+ regulatory T cells was detected. Foxp3-mRNA expression correlated positive with the level of IFN-γ and TGF-β, the percentage of CD4+CD25+ regulatory T cell correlated positive with the level of IFN-γ and TGF-β. Foxp3-mRNA expression and the percentage of CD4+CD25+ regulatory T cell had no correlation with the levels of IL-4 and IL-10. 5 . There were more cells in asthmatic children induced sputum than in normal children. The number of sputum neutrophil was higher in exacerbation children than in remission children and in normal children. The number of sputum lymphocyte was higher in remission children than in exacerbation and in normal children. The difference of sputum eosinophil was not found in each group. 6 . The levels of sputum supernatant IL-8 and IL-9 were significantly higher in asthmatic children than in normal children. A significant positive correlation between the levels of IL...
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