Human skin and oral mucosal dendritic cells as 'good guys' and 'bad guys' in allergic immune responses.

Recent progress achieved by an impressive number of studies focusing upon the ontogenesis and immunobiology of epidermal Langerhans cells (LCs) and other cutaneous dendritic cell (DC) populations as well as DCs at oral mucosal tissue has profoundly revised our understanding of the role of DCs in different tissues and microenvironments. By sensing their environment for microbial signals or allergens and bridging innate and adaptive immunity in a sophisticated manner, subtypes of DCs play a critical role in the maintenance of the immunological homeostasis in the periphery. Thereby, DCs, located directly at the interface to the environment, fulfil opposing tasks as they are key players in both the control and the generation of allergic inflammation. Furthermore, it is under ongoing debate whether DCs attenuate or aggravate allergic inflammation. As a consequence, accumulated knowledge gained in this field within the last few years has provided an excellent basis for innovative therapeutic opportunities which tend to target specifically the multi-faceted properties of DCs at distinct anatomical sites.