16HBE14o- is a human bronchial epithelial cell line isolated from a 1-year old male heart-lung patient and immortalized with the origin-of-replication defective SV40 plasmid (pSVori-). The cell line retains characteristic features of normal differentiated bronchial epithelial cells including a cobblestone morphology, cytokeratin expression, the ability to form tight junctions, and directional ion transport. When grown with an air/liquid interface, cilia can be detected. In contrast to most other respiratory cell lines, 16HBE14o- expresses high levels of cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and protein. Expression of CFTR is correlated to cAMP-dependent Cl- conductance in a variety of cells, including 16HE14o- epithelial cells.