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a Center for Experimental Pathology, Cantonal Institute of Pathology, 6601 Locarno, Switzerland
Key Words: sympathetic nervous system • dendritic cells • epidermal keratinocytes • innate immunity • adaptive immunity • toll-like receptors • adrenergic receptors • T cell priming • CD4+ • CD25+ • regulatory T cells • autoimmune diseases
Address for correspondence: Georges J.M. Maestroni, Center for Experimental Pathology, Cantonal Institute of Pathology, PO Box, 6601 Locarno, Switzerland. Voice: 41-91-816-07-91; fax: 41-91-816-07-99. e-mail: georges.maestroni{at}ti.ch
Our studies focused on the sympathetic nervous system (SNS) influence on dendritic cells (DCs), which play a crucial role in the innate immune response. We found that DCs express a variety of adrenergic receptors (ARs) with
 1-ARs playing a stimulatory and  2-ARs an inhibitory effect on DCs migration. 2-ARs in skin and bone marrow-derived DCs when stimulated by bacterial toll-like receptors (TLRs) agonists respond to norepinephrine (NE) by decreased interleukin-12 (IL-12) and increased IL-10 production which in turn downregulates inflammatory cytokine production and CCR7 expression and thus their migration ability leading to reduced T helper-1 (Th1) priming. 1, 2 We also found that contact sensitizers that may induce a predominant Th1 response, do so by inhibiting the local NE turnover in the skin.3 The SNS seems therefore to contribute in shaping the information conveyed by DCs to T cells and thus in inducing the appropriate adaptive immune response. In this sense, the SNS physiological influence may allow Th2 priming to fight infections sustained by extracellular pathogens and limit the risk for organ-specific autoimmune reactions associated with excessive Th1 priming and inhibition of T regulatory cell functions. More recently, we found that preconditioning of the skin by -adrenergic antagonist and the TLR2 agonist S. Aureus peptidoglycan (PGN) may instruct a Th1 adaptive response to a soluble protein antigen. On the contrary, when the TLR4 agonist E. Coli lipopolysaccharide was used, the presence of the -adrenergic antagonist was not effective. These effects were consonant with the pattern of TLRs expression shown by epidermal keratinocytes (EKs) but not by skin DCs. As -ARs signaling defects 4, 5, 6 together with S. Aureus infections7 are thought to serve as initiation and/or persistence factors for numerous Th1-sustained autoimmune inflammatory skin diseases, we might have disclosed at least part of the relevant pathogenetic mechanism.
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