Epithelial models to study food allergen-induced barrier disruption and immune activation

Changes in lifestyle, diet and environmental factors in westernized countries correspond with the rise in non-communicable diseases affecting metabolic and immune disorders, such as allergies. Therefore the mechanisms by which environmental factors and allergens are capable of elicitating allergic sensitization need to be further unraveled. In vitro models using human epithelial cells, with or without immune cells, are needed to achieve this purpose. Epithelial cells cover mucosal surfaces and provide a barrier between the external and internal environment. In mucosal tissues such as the respiratory and gastro-intestinal tract, epithelial cells not only contribute to barrier integrity but also actively regulate dendritic cell function and adaptive immune responses and can support tolerance induction or allergic sensitization. Certain allergens contain protease activity which may facilitate them to cross the barrier, others are transported via transcytosis. In addition, certain allergens may provoke epithelial activation resulting in production of T_H2 driving immune mediators. Preserving epithelial homeostasis is important to suppress allergic sensitization. This review describes in vitro models of human intestinal epithelial cells and co-culture models that are currently available to determine barrier disruption or immune activation induced by food allergens. These can be used for future development of in vitro models to study the contribution of intestinal epithelial cells in allergic sensitization and to identify sensitizing properties of novel proteins.