Increased frequency of dual-positive TH2/TH17 cells in bronchoalveolar lavage fluid characterizes a population of patients with severe asthma

Abstract

TH2 cells can further differentiate into dual-positive TH2/TH17 cells. The presence of dual-positive TH2/TH17 cells in the airways and their effect on asthma severity are unknown. We sought to study dual-positive TH2/TH17 cells in bronchoalveolar lavage (BAL) fluid from asthmatic patients, examine their response to glucocorticoids, and define their relevance for disease severity. Bronchoscopy and lavage were performed in 52 asthmatic patients and 25 disease control subjects. TH2 and TH2/TH17 cells were analyzed by using multicolor flow cytometry and confocal immunofluorescence microscopy. Cytokines were assayed by means of ELISA. Dual-positive TH2/TH17 cells were present at a higher frequency in BAL fluid from asthmatic patients compared with numbers seen in disease control subjects. High-level IL-4 production was typically accompanied by high-level IL-17 production and coexpression of GATA3 and retinoic acid receptor-related orphan receptor γt. Increased presence of TH2/TH17 cells was associated with increased IL-17 production in lavage fluid. TH2/TH17 cell counts and IL-17 production correlated with PC20 for methacholine, eosinophil counts, and FEV1. TH2/TH17 cells, unlike TH2 cells, were resistant to dexamethasone-induced cell death. They expressed higher levels of mitogen-activated protein-extracellular signal-regulated kinase kinase 1, a molecule that induces glucocorticoid resistance. On the basis of the dominance of BAL fluid TH2 or TH2/TH17 cells, we identified 3 subgroups of asthma: TH2(predominant), TH2/TH17(predominant), and TH2/TH17(low). The TH2/TH17(predominant) subgroup manifested the most severe form of asthma, whereas the TH2/TH17(low) subgroup had the mildest asthma. Asthma is associated with a higher frequency of dual-positive TH2/TH17 cells in BAL fluid. The TH2/TH17(predominant) subgroup of asthmatic patients manifested glucocorticoid resistance in vitro. They also had the greatest airway obstruction and hyperreactivity compared with the TH2(predominant) and TH2/TH17(low) subgroups.