Evidence of regulatory myeloid dendritic cells and circulating inflammatory epidermal dendritic cells-like modulated by Toll-like receptors 2 and 7/8 in adults with atopic dermatitis

Backgroud Atopic dermatitis (AD) is a chronic, inflammatory skin disease characterized by intense pruritus and xerosis. Dendritic cells (DC) play an essential role in tissue inflammation in atopic dermatitis (AD) skin, especially the inflammatory epidermal dendritic cells (IDEC), a particular subset of myeloid dendritic cells (mDC). The aim of the present study was to assess the phenotype and function of mDC and circulating IDEC-like in peripheral blood mononuclear cells (PBMC) of adults with AD. Methods We selected 21 AD patients and 21 non-AD controls, age and gender matched. Expressions of Fc epsilon RI, CD36, TNF, IFN-gamma , and IL-10 in mDC were analyzed by flow cytometry under various stimuli, such as staphylococcal enterotoxin B (SEB), TLR2 (Pam3CSK4), TLR4 (LPS), and TLR7/8 (CL097) agonists. Results The most prominent findings in AD patients were: (i) enhanced frequency of IL-10 under TLR4 (LPS), and decreased frequency of IFN-gamma and TNF under TLR2 (Pam3CSK4) and 7/8 (CL097) stimulation in classic mDC; (ii) elevation of circulating IDEC-like frequency with TLR2 (Pam3CSK4) stimuli, augmented frequency of IFN-gamma in nonstimulated condition, and of IL-10 under TLR7/8 (CL097) stimuli in IDEC-like population. Conclusions In AD individuals, classic mDC showed an immunomodulatory profile, favoring tolerance in a combined action with IDEC-like, and inducing Th1 polarization. Our findings indicate a potential role of IDEC-like in the maintenance of inflammation in atopic dermatitis patients; moreover, IDEC-like may exert a regulatory impact on T cells of AD individuals through IL-10, often induced by agonist mimicking single stranded RNA virus. (AU)