Human airway epithelial cell innate immunity: relevance to asthma

The innate immunity function of the human airway epithelium is responsible for orchestrating defence against inhaled viruses, bacteria, fungi, allergens, pollution, and other environmental insults. Epithelial cells present a mechanically tight, pseudostratified, multi-cell barrier that secretes mucus, surfactants, and anti-microbial peptides to manage minor insults. Secondary to the mechanical impedances, cell surface and cytoplasmic pattern recognition receptors await detection of more aggressive insults. The differentiation state of the airway epithelium contributes to innate immunity by compartmentalizing receptors and mediator production. Activation of innate immune receptors triggers production of interferons, cytokines, and chemokines, which influence adaptive immune responses. Mounting evidence suggests that these responses are aberrant in asthma and may contribute to disease progression and exacerbations. In this review, we discuss the recent evidence supporting these statements, focusing primarily on data generated from using human samples.