Bronchial Epithelial Cells in Allergic Reactions

Bronchial epithelial cells (BEC) are known to play an integral role in the airway defense mechanism via mucociliary system as well as mechanical barriers. Recent studies further indicate that BEC produce and release biologically active compounds including lipid mediators, growth factors, endothelin and a variety of cytokines/chemokines important in the pathogenesis of airway disorders. Cytokines and chemokines produced by BEC include IL-6, IL-8, G-CSF, GM-CSF, RANTES, eotaxin and TARC. Pro-inflammatory cytokines IL-1 and TNF-α, generally upregulate expression and release these cytokines/chemokines. BEC from patients with bronchial asthma showed increased levels of mRNA for these potent inflammatory peptides. BEC also interact with immune and inflammatory cells by direct adhesion as well as by humoral factors including cytokines. For example, eosinophil adhesion to BEC may be an important signal for the activation and degranulation of eosinophils. BEC is also believed to take part in the airway mucosal immunity via Toll-like receptors. Finally, BEC may play a crucial role in the processes of airway remodeling by cross-talk with mesenchymal cells. These findings strongly suggest that BEC are actively involved as regulators of allergic inflammatory responses, and become a target for therapeutic intervention.