Introduction

Nowadays, we appreciate the many functions that epithelial cells display to maintain lung and airway homeostasis. Epithelial cells are well differentiated and polarised, which allows them to directly counter local challenges and also to recruit help by interacting with other structural and migratory cells. However, our knowledge of the functioning of epithelial cells under pathophysiological conditions and how that may contribute to the pathophysiology is scanty. Following on from a European Respiratory Society Research Seminar in which we addressed the issue of epithelial functioning under normal and pathophysiological conditions, it was felt timely to provide an update on the topics discussed, as well as two in-depth reviews addressing new and exciting developments in this field.