CFTR and cystic fibrosis: In order to investigate the risk factors that lead to Af invasion in CF-LTRs, we developed a CF-OTT model by transplanting a trachea from a Balb/c mouse into a CFTR−/− recipient mouse (Cftrtm1Unc Tg(FABPCFTR)1Jaw on a C57Bl/6 background).