Insight into newly discovered innate immune modulation in atopic dermatitis.

Atopic dermatitis (AD) is a highly pruritic, chronic relapsing inflammatory skin disease characterized by innate and adaptive immune reactions. In AD, innate immune mechanisms such as pattern recognition receptors and antimicrobial peptides have been investigated in detail, but recently, epidermis-derived cytokines, namely thymic stromal lymphopoietin (TSLP), IL-25 and IL-33, were shown to participate in innate immune reactions independently of adaptive immunity. In addition to conventional innate cells, such as mast cells, basophils and eosinophils, Th2 cytokine-producing invariant natural killer T (iNKT) cells, innate lymphoid cells (ILCs) and Th17/Th22 cytokine-producing innate cells - iNKT cells and natural killer (NK)-like cells - can participate in innate immune modulation in AD. Accordingly, early control of innate immune responses in AD before activation of adaptive immune responses by conventional T and B cells that perpetuate chronic skin inflammation may adequately alleviate acute exacerbations of AD. Therefore, we hypothesized that select immune modulators targeting the innate immune response could potentially be used for individualized treatment of AD.