CXCL8 and cystic fibrosis: However, at those concentrations of LPS (i.e., ≥15,000 ng/mL) frequently present in the sputum of CF patients with chronic P. aeruginosa lung infection33, the level of released IL-8 dropped down to 50 or 100 pg/mL for wt-CFBE and F508del-CFBE, respectively (Fig. 6a).