Methods: Twenty-eight children with exacerbated asthmatics without using any corticosteroids were divided into three groups: eosinophilic asthma group (EA group) (n = 12), neutrophilic asthma group (NA group) (n = 10) and paucigranulocytic asthma (PGA group) (n = 6) according to induced sputum cytology.Ten healthy children were recruited as healthy control group (HC group) (n =10). Th17,Th2 cells in peripheral blood and Ki-67,STAT5, BCL-2 expressed in Th17 cells were detected by flow cytometry. Expression of RORγt-mRNA in peripheral blood mononuclear cell (PBMC)was detected by real-time quantitative polymerase chain reaction .Concentrations of IL-17, IL-8 and IL-5 in induced sputum supernatant, as well as concentrations of IL-17 in plasma and in the culture supernatant from PMA-stimulated PBMC were measured by enzyme linked immunosorbent assay.
Results: The percentage of Th17, Ki-67+Th17 , STAT5+Th17 , BCL-2+Th17 cells in peripheral blood and expression level of RORγt-mRNA in PBMC were significantly higher in NA group than in EA group , PGA group and HC group (both P<0.01). The level of IL-17 and IL-8 in sputum and level of IL-17 in culture supernatant from PMA-stimulated PBMC were significantly higher in NA group than in EA group , PGA group and HC group (both P<0.01). The percentage of Th2 cells in peripheral blood and level of IL-5 in sputum supernatant were significantly higher in EA group than in NA group , PGA group and HC group (both P<0.01). The percentage of Th17 cells in peripheral blood, the levels of IL-17 in sputum and PBMC culture supernatant ,and the level of IL-8 in sputum supernatant were all correlated positively with the percentage of neutrophils in sputum.
Conclusions Both Th17 cells and Th2 cells are involved in the pathogenesis of asthma in children. Th17 cells and IL-17 may mediate neutrophilic airway inflammation in asthma，indicating an important role for Th17 cells in childhood neutrophilic asthma. Th17 cells may be maintain their survival through activation of the JAK/STAT5 signaling pathway.