Introduction: The pathophysiology of both cystic fibrosis (CF) lung disease and lung allograft injury following transplantation involves neutrophilic inflammation, which is associated with increased levels of the neutrophil chemokine interleukin(IL)-8.^1,2 Bile acid aspiration, as a result of duodeno-oesophageal reflux, has been implicated as a common and emerging aspect of lung injury.³ In this study we have evaluated the effect of bile acid challenge on primary bronchial epithelial cells derived from patients with CF and from lung allografts. Methods: Cultures of primary bronchial epithelial cells were established from bronchial brushings from lung transplant recipients and from cystic fibrosis lungs removed at the time of transplantation, as described previously (see Forrest et al.⁴ and Brodlie et al.⁵). Epithelial cell cultures were stimulated with different primary and secondary bile acids, namely cholic and chenodeoxycholic acid, deoxycholic and lithocholic acid and taurodeoxycholic and taurocholic acid, at the physiologically achievable concentrations of 1, 5 10, 25 and 50 μmol/L. IL-8 was then measured in the culture supernatants by enzyme-linked immunosorbent assay at 48 hours post-stimulation (MesoScale Discovery). Cell viability was assessed at the end of each experiment (CellTiter-Blue, Promega). Differences in IL-8 production from control, unstimulated conditions were compared using a non-parametric paired t-test (Prism, GraphPad). Results: Detailed results are presented for stimulation with lithocholic acid as this was the most effective. Stimulation of bronchial epithelial cells from people with CF (n=7) and lung allografts (n=7) with lithocholic acid at 1, 5, 10 and 25 µmol/L resulted in a significant increase in IL-8 production compared to control, unstimulated conditions (p<0.05). Treatment with 50 µmol/L lithocholic acid resulted in >90% cell death. Figure 1 displays IL-8 production, expressed as increase from unstimulated conditions, by bronchial epithelial cells from people with CF and lung allografts following treatment with different concentrations of lithocholic acid. Conclusion: Primary bronchial epithelial cell data may be used to explore potential mechanisms in the pathogenesis of CF lung disease and lung allograft injury. Airway epithelial cells up regulate IL-8 production when exposed to lithocholic acid and our data indicate a possible mechanism whereby aspiration of bile acids, as a result of duodeno-oseophogaeal reflux, may be linked to neutrophilic inflammation in CF lung disease and lung transplant injury. The translational significance of this finding is that reflux may be treated and essentially prevented by fundoplication procedures.