Interactions between epithelial cells and dendritic cells in airway immune responses: lessons from allergic airway disease

Abstract

Micro‐organisms constantly invade the human body and may form a threat to our health. Traditionally, concepts of defence mechanisms have included a protective outer layer of epithelia and a vigilant immune system searching for areas where the integrity of the outer layer may be compromised. Instead of considering these elements as two independent mechanisms, we should be treating them as a single integrated system. This review will present and discuss the role of local immune‐competent cells and local epithelia in the recognition of potential pathogens and how the interaction between the two components may affect the initiation of the airway immune response. A concept emerges where airway mucosal dendritic cells act as integrators of both immunostimulatory and immunosuppressive signals that act within actively‐involved mucosal tissue.

E-cadherin: gatekeeper of airway mucosa and allergic sensitization

“…Importantly, disruption of E-cadherin-mediated adhesion induces typical features of DC maturation, including the upregulation of co-stimulatory molecules, MHC class II, and chemokine receptors. A similar role for these E-cadherinmediated interactions has been described in epidermal Langerhans cells (LCs) [33,37].…”

Primary Human mDC1, mDC2, and pDC Dendritic Cells Are Differentially Infected and Activated by Respiratory Syncytial Virus

“…This may be reflected in the diversity of DC phenotypes found at the mucosa of specific tissues and within different compartments of a single organ [72], [73]. DC precursors and immature DCs in the lung respond to factors secreted by resident epithelial and innate cells, resulting in differentiation and activation [72]–[76]. Monocytes residing in the respiratory tract have been suggested as a local precursor for pulmonary DCs, particularly maintaining homeostatic balance [72], [73], [75].…”

Innate immunity in allergic disease

“…There is a close relationship between populations of airway APCs and airway ECs, one that serves to maintain homeostasis, moderate innate and adaptive immune responses, and return the lung to its normal steady‐state condition (123). Airway ECs express PRRs as well as receptors for cytokines produced during inflammation.…”

“…Interest has focused on the production of thymic stromal lymphopoietin (TSLP) by respiratory ECs and other cells. TLSP has been shown to polarize APCs to drive Th2‐mediated immune responses, although the role of TSLP in asthma and allergic rhinitis has yet to be fully characterized (123, 125). TSLP activates cDC to secrete CCL17 thereby facilitating Th2 cell recruitment into the inflamed airways (126).…”