Goblet and Clara cells of human distal airways: evidence for smoking induced changes in their numbers.

The goblet cell and Clara cell populations of human distal airway epithelium were examined. The bronchioles, terminal bronchioles, and respiratory bronchioles of 16 smokers and four non-smokers were studied by both light and electron microscopy in surgically resected specimens. A very significantly (p less than 0.001) greater number of goblet cells were found in the bronchioles of smokers compared than in those of non-smokers but no such difference was evident in terminal/respiratory bronchioles. Clara cell numbers in contrast were lower in the bronchioles (p less than 0.01) and terminal and respiratory bronchioles of smokers (p less than 0.01). Both of these alterations in cell frequency may adversely affect small airway function in smokers.