Neutrophilic inflammation and its resolution in CF airways. A) Time course of BAL neutrophils after CNP instillation showing a slower decline of BAL neutrophils from days 1 to 7 in Cftr mutant compared to WT mice. *: significant difference to WT animals, p < 0.05. B) Mode of action for impaired inflammation resolution in CF airways. The accumulation of inflammatory cells (PMN) in Cftr mutant lungs at day 3 after particle exposure is probably supported by different pathways: Augmented CXCL5 levels, released from Cftr mutant inflammatory epithelial cells, enhance exposure-related PMN recruitment and accumulation on the airway surface. In addition, elevated G-CSF and reduced 15-HETE levels in Cftr mutant lungs contribute to prolonged PMN survival and impaired efferocytosis of apoptotic PMN by macrophages. PMN: Polymorphnuclear cells = neutrophils, AM: Airway macrophages, AEC: airway and alveolar epithelial cells, EC: endothelial cells.