Interactions between dendritic cells and epithelial cells in allergic disease

Dendritic cells (DCs) play a crucial role in the sensitisation process. Upon encounter with an allergen, DCs require interactions with other cells and factors for triggering a primary or secondary immune response. Epithelial cells (ECs) express features of accessory cells, Such as expression of HLA-DR, co-stimulatory molecules, functional Fc gamma R, molecules of the antigen-processing machinery, and display an ability to internalise antigen. These features may authorize them to function as immunomodulators (e.g. amplification of memory T cells during secondary immune responses). ECs may increase chemokine (e.g. CCL20) secretion thereby attracting DCs. Epithelial human TSLP activates DC, which allow them to prime naive T cell, for the production of pro-inflammatory cytokines, while down-regulating IFN-gamma and IL-10. ECs may also influence the local polarization of types 1 and 2 antigen-presenting cells via PGE(2) by impairing the ability of maturing DC to produce bioactive IL-12 p70. PGE(2) is synergistic with IL-1 beta and TNF-alpha in the induction of functional and phenotypic maturation of DC and induce IL12 p40 production. Sensitisation via the respiratory route may be Th-2 skewed, possibly because the antigen recognition by DC occurs in an environment rich of airway EC-product such its PGE(2). (c) 2005 Elsevier Ireland Ltd. All rights reserved.