In CF, neutrophils are the predominant immune cells infiltrating the airway mucosa and the intralumenal space of bronchioles (accounting for ~70% of the total cell count in BAL fluid) driven by IL-8 and IL-17 secretion; their load as well as the extracellular activity of the protease NE in BAL fluid correlates well with disease progression in CF patients, from infancy to adulthood [71,72,73]. The gene discussed is IL17A; the disease is cystic fibrosis.