Neutrophilic infiltration is driven by increased IFNγ and/or IL‐17A production, and IFNγ and IL‐17A were increased in bronchoalveolar lavage (BAL) fluid and in CD4 and CD8 T cells of patients with severe asthma compared to controls or milder asthma phenotypes [15, 16, 17, 18, 19, 20, 21]. Here, IL17A is linked to asthma.