Atopic dermatitis: A tale of two distinct pathomechanisms that make you itch.

Atopic dermatitis (AD) or eczema is the most common chronic inflammatory skin disease. It is a multifactorial disease with local and systemic immune changes. Current therapies focus on restoring the local skin barrier or inhibiting immune responses. In this issue of the European Journal of Immunology, Sehra et al. [Eur. J. Immunol. 2016. 46:2609-2613] describe a mouse model with T-cell-specific expression of constitutively active Stat6 in Flaky tail mice, which have mutations in the Flg and Tmem79 genes. The authors describe that it is the combination of changes in the skin barrier proteins filaggrin and Tmem79, together with Th2 cytokine signaling in the constitutively active Stat6 transgene, that drives the immune-pathomechanism in AD. These results are consistent with human studies where it is demonstrated that diminished filaggrin expression in skin is a predisposing factor for AD, but is neither required nor sufficient for disease indicating that additional factors are required for disease development. The current mouse model by Sehra et al. could be instrumental in evaluation new therapeutic strategies for AD.