Epithelial cells as regulators of airway inflammation

The past decade has seen major advances in our understanding of the metabolic and biochemical functions of the epithelial cell. As a result, the traditional view of the epithelium as a relatively passive physical barrier to the external environment has been superseded by the concept that the epithelial cell plays a key role in regulating airway inflammation. The epithelial cell exerts this modulatory effect in several ways. Epithelial cells can function to maintain mucosal integrity and to modulate local immune responses. They can also limit inflammatory processes by degrading, or inhibiting, proinflammatory mediators and proteins. However, the epithelium also responds to a range of stimuli by producing biologically active mediators that can influence airway inflammation. These include, but are not limited to, a broad range of cytokines and chemokines that can exert profound effects on inflammatory cells, as well as lipid and peptide mediators. This review will highlight some of these aspects of the role of the epithelium in regulating airway inflammation.