CFTR and cystic fibrosis: As a source for polyA + RNA, we used T84 cells, which are derived from colon carcinoma, 16HBE14o-cells, which are virus-transformed non-CF respiratory epithelial cells, and CFBE41o- and CFTE29o-cells, both of which are immortalized respiratory epithelial cells derived from F508del-CFTR homozygous CF patients.