Interestingly, increased levels of anti-inflammatory Th2 cytokines (IL-5 and IL-13) and antibacterial Th17 cytokine (IL-17A) are observed in bronchoalveolar lavage (BAL) fluid of CF patients chronically colonized or infected with P. aeruginosa (Moser et al., 2000; Hartl et al., 2006; Tiringer et al., 2013). This evidence concerns the gene IL17A and cystic fibrosis.