Cystic fibrosis (CF)is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and is the most common inherited life-limiting disease in North European people. Next to epithelial cells, CFTR expression has been demonstrated in cells of the innate and adaptive immune system and has shown to be critical for normal function. Approximately 60% of CF patients are infected with Aspergillus fumigatus, and its presence has been associated with accelerated lung function decline. Our work is focussing on the interaction between A. fumigatus and CF epithelial and immune cells with an aim to prevent lung damage caused by A. fumigatus in the airways.