Thereby, IL-17A sputum levels are negatively correlated with airway responsiveness to methacholine [44], while IL-17A expression levels in bronchial biopsies correlate with the degree of airway neutrophilia [36,41,45] and are more pronounced in patients with moderate-to-severe or exacerbation-prone asthma than in those with mild-to-moderate asthma [36,40,42,46,47]. Here, IL17A is linked to asthma.