Unique role of allergens and the epithelium in asthma

The respiratory epithelium has been regarded as an inert barrier separating the human airway from the external world. Equally allergens have been perceived to be environmental proteins which interact with immunocompetent cells, activate inflammatory cells via IgE and promote the allergic response. However many allergens are biochemically active and are able to increase epithelial permeability and to stimulate epithelial cells to produce cytokines, adhesion receptors and MHC Class II expression. Thus the biochemical properties of allergens are likely to be important in enhancing the allergic responses and disease.