Altered expression of regulatory T and Th17 cells in murine bronchial asthma

Alteration of the careful balance of the ratio of Th1/Th2 cell subsets impacts immune function and plays an important role in the pathogenesis of asthma. There is little research on the impact of changes on the balance of the regulatory T (Treg)/Th17 subset ratio and its possible repercussions for asthma. This investigation used a murine model of asthma to measure the expression levels of Treg and Th17 cells and the levels of their transcription factors Foxp3 and retinoic acid receptor-related orphan nuclear receptor (ROR)γt in bronchial asthma while assessing indexes of airway inflammation. Thirty female SPF BALB/c mice were divided into three equally numbered groups: a normal control, an asthma and a dexamethasone treatment group. All the airway inflammation indexes measured were more prominent in the asthma group and less so in the control group. The percentage of the lymphocyte subset CD4⁺CD25⁺Foxp3⁺ cells in the CD4⁺ cells in the asthma group was significantly lower than that in the normal control group (P<0.01). The percentage of the lymphocyte subset CD4⁺IL-17⁺ cells in the CD4⁺ cells in the asthma group was significantly higher than that in the normal control group (P<0.01). The ratio of CD4⁺CD25⁺Foxp3⁺ cells/CD4⁺IL-17⁺ cells in the asthma group decreased compared with that in the normal control group (P<0.01). The expression level of Foxp3 of the mice in the asthma group was significantly lower than that in the control group (P<0.01). The expression intensity of RORγt in the asthma group was higher than that in the normal control group (P<0.01). Finally, the Foxp3/RORγt protein expression ratio in the asthma group was significantly lower than that in the normal control group (P<0.01). The Foxp3/RORγt protein expression ratio and the airway responsiveness were negatively correlated. The average levels of inflammation markers in the dexamethasone group were intermediate between the other groups. During the course of bronchial asthma the unbalanced expression of Treg and Th17 affects mostly the expression of Foxp3/RORγt, leading to inflammation of the airways. Dexamethasone may inhibit airway inflammation by regulating the balance between Treg and Th17.