Background: The pathogenetic mechanisms of neutrophilic asthma are not well understood now. Whether T helper (Th)17-mediated immunity contributes to the pathogenesis of neutrophilic asthma in human is still under investigation. The aim of this study was to explore the relationship between Th17-mediated immunity and airway inflammation in childhood neutrophilic asthma.
Methods: Twenty-eight children with exacerbated asthma and without using any glucocorticoids were divided into three groups: eosinophilic asthma (EA, n = 12) group, neutrophilic asthma (NA, n = 10) group and paucigranulocytic asthma (PGA, n = 6) group according to the induced sputum cytology. Ten healthy children were recruited as healthy control (HC, n = 10) group. Peripheral Th17 and Th2 cells, and the expression of Ki-67 in peripheral Th17 cells were detected by flow cytometry. The mRNA expression of retinoic acid-related orphan receptor γt (RORγt) in peripheral blood mononuclear cells (PBMCs) was detected by qRT-PCR. The concentrations of IL-17, IL-8 and IL-5 in sputum, as well as IL-17 in plasma and culture supernatant of activated PBMCs were measured by ELISA.
Results: The percentage of Th17 cells in peripheral Th cells, and the concentrations of IL-17, IL-8 in sputum, as well as IL-17 in culture supernatant of activated PBMCs were all increased in NA group, and positively correlated with neutrophil level in sputum and with each other. Also, the mRNA expression of RORγt in PBMCs and Ki-67 positivity in peripheral Th17 cells were both increased in NA group. The percentage of Th2 cells in peripheral Th cells, and the concentration of IL-5 in sputum were both increased in EA group, and positively correlated with eosinophil level in sputum and with each other.
Conclusions: Both Th17- and Th2-mediated immunity are involved in the pathogenesis of childhood asthma. There is predominance of Th17-mediated immunity and Th17 cells proliferation in childhood neutrophilic asthma.
Keywords: Asthma; Children; IL-17; Neutrophils; Th17 cells.