DC-SIGN promotes allergen uptake and activation of dendritic cells in patients with atopic dermatitis

Background: Atopic dermatitis (AD) is a common inflammatory skin disease, concomitant with allergic reactions to allergens. However, the exact mechanisms of allergen-induced immune responses in AD are not clear. The aim of this study is to explore the role of DC-SIGN in capturing and processing glycan-containing allergens and in the subsequent DC activation and T helper cell polarization in AD patients. Methods: DC-SIGN expression on DCs from AD patients was analysed by confocal microscopy and flow cytometry. DC-SIGN binding to common allergens was determined by ELISA. Activation of monocyte-derived dendritic cells (Mo-DCs) by allergens was analysed by evaluation of pro-inflammatory cytokines production, and their impact on T-cell responses was investigated by a DC-T cell coculture. Results: DC-SIGN expression was higher on DCs in the lesional skin of AD patients compared with that of healthy controls and was correlated with disease severity. DC-SIGN could bind to many common allergens including house dust mite allergen (Der p2) and egg white allergen (Gal d2). Mo-DCs showed measurable expression of DC-SIGN and a concentration-dependent uptake of Der p2 and Gal d2, which was inhibited by mannan and anti-DC-SIGN Abs. Der p2 and Gal d2 induced the production of pro inflammatory cytokines, including TNF-alpha. and IL-6, by DCs from AD patients and facilitated Th2 and Th22 cell polarization. Conclusions: Binding of common allergens by DC-SIGN on DCs may initiate allergen sensitization of AD or provoke the relapse of AD. Regulating the allergen-DC-SIGN interaction might be a promising strategy to prevent or intervene in the progress of AD. (C) 2016 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.