Inactivation of the interleukin-22 pathway in the airways of cystic fibrosis patients.

Interleukin (IL)-22 plays a critical role in regulating the maintenance of the mucosal barrier. As airway epithelial regeneration is abnormal in cystic fibrosis (CF), we investigated IL-22 integrity in CF. We first demonstrated, using Il-22-/- mice, that IL-22 is important to prevent lung damage induced by the CF pathogen Pseudomonas aeruginosa. Next, IL-22 receptor was found normally expressed at the airway epithelial surfaces of CF patients. In wound-healing assays, IL-22-treated CF cultures had higher wound-closure rate than controls, suggesting that IL-22 signaling per se could be functional in a CF context. However, persistence of neutrophil-derived serine-proteases is a major feature of CF airways. Remarkably, IL-22 was found altered in this protease-rich inflammatory microenvironment; the serine protease-3 being the most prone to fully degrade IL-22. Consequently, we suspect an acquired deficiency of the IL-22 pathway in the lungs of CF patients due to IL-22 cleavage by the surrounding neutrophil serine-proteases.