Airway epithelium and structural cells
The respiratory system airway epithelium has defence mechanisms to protect itself. The physical barrier that stops penetration by inhaled microbes/allergens is maintained by intercellular epithelial junctions. Only extremely small particles, less than 3 to 5 microns (0.000118 to 0.000196 inches) in diameter, penetrate to the deep lung. Any compromise on epithelial integrity predisposes to aeroallergen sensitization and ongoing inflammation by allergens and microbes.1
The airway epithelial cell innate immune function is however impaired in children with persistent wheeze compared with healthy children. Airway remodelling from inflammation increased thickness of the subepithelial reticular basement membrane, increased airway smooth muscle angiogenesis. The airway remodelling linked with abnormal lung function in older children with asthma and likely associated with early lung function changes.