Nasal IL-17F is related to bronchial IL-17F/neutrophilia and exacerbations in stable atopic severe asthma

Severe asthma (SA) is associated with neutrophil recruitment and T helper (T_H)17 chemokine overexpression in bronchial biopsies. We aimed to evaluate IL-17A and IL-17F expression in nasal/bronchial lamina propria of atopic mild-to-severe asthmatics and controls in relation to neutrophilia and asthma exacerbations. Cryostat sections of nasal/bronchial biopsies obtained from 14 SA and 14 mild asthma (MA) stable atopic patients with rhinitis, and seven healthy controls were analyzed by immunohistochemistry for neutrophils, IL-17A and IL-17F expression. Atopic SA showed an increase in asthma exacerbations number, IL-17F and IL-17A expression in nasal/bronchial lamina propria compared to MA and controls, and a higher expression of bronchial neutrophils in SA compared to MA and controls. In all asthmatics, significant relationships were found between bronchial IL-17F and neutrophils/FEV₁, nasal IL-17F and bronchial neutrophil/IL-17 markers and between the latter and exacerbations, suggesting that nasal IL-17F might be informative on bronchial IL17-driven neutrophilia in atopic SA.