differentiate under the control of FOXJ1 into ciliated cells; and into secretory cells under the control of Notch signalling, and the transcription factors SPDEF and FOXA3. The regeneration of cells can be normal or in the case of smokers the regeneration may be of altered histologic phenotypes.

Basal cells can also provide a defence function upregulating innate immune mediators such as RNase7, an antimicrobial protein. RNase7,