Background: Respiratory allergen contact is the critical event in the elicitation and boosting of allergen-specific immune responses, as well as in the induction of immediate and late inflammatory reactions.
Objective: We sought to investigate the influence of various factors of allergic inflammation on the integrity and barrier function of respiratory epithelium for allergens.
Methods: We cultured the human bronchial epithelial cell line 16HBE14o- in a transwell culture system as a surrogate of intact respiratory epithelium and used purified iodine 125-labeled recombinant major birch pollen allergen (rBet v 1) to study the extent, kinetics, and factors influencing transepithelial allergen penetration.
Results: Culture supernatants from activated allergen-specific T H 1 clones decreased transepithelial resistance. A screening of various factors (histamine, IFN-gamma, IL-1beta, IL-2, IL-3, IL-4, IL-5, IL-8, IL-12, and TNF-alpha) identified IFN-gamma as a potent factor capable of reducing epithelial barrier properties and enhancing transepithelial allergen penetration. Increased submucosal allergen concentrations caused by IFN-gamma-mediated reduction of epithelial barrier function provoked a more than 7-fold augmentation of histamine release from sensitized basophils.
Conclusion: These results demonstrate that the T H 1 cell-derived cytokine IFN-gamma facilitates allergen penetration through the respiratory epithelium and thereby can aggravate allergic inflammation.