MMP9 and cystic fibrosis: In a study conducted by Taylor et al. on a cohort of F508del CF subjects, authors found elevated levels of IL-17, NE, and MMP9 in sputum at the time of pulmonary exacerbation due to P. aeruginosa infection with decreased levels of IL-17 IV antibiotics; furthermore IL-17 producing neutrophils were the predominant cell in sputum of that cohort during the pulmonary exacerbation and a statistically significant inverse correlation between them and FEV1 was demonstrated [75].