γδ T cells and inflammatory skin diseases

Approximately 25% of the population suffers from skin diseases. The most common forms of skin diseases are the inflammatory skin diseases such as allergic contact dermatitis, psoriasis, and atopic dermatitis. These diseases are described as T cell-mediated diseases induced by either allergens or autoantigens. Classically, the focus has been on the role of alpha beta T cells, but it is becoming increasingly clear that gamma delta T cells play a central role in inflammatory skin diseases. In particular, an important role of IL-17A-producing gamma delta T cells in these inflammatory skin diseases has been shown in various disease models in mice. Interestingly, various epidermal proteins, which appear to be linked to inflammatory conditions in the skin by yet undescribed mechanisms, are expressed by specific subsets of thymic epithelial cells and mutations in these proteins seem to affect gamma delta T cell development. The focus of this review is how mutations in epidermal proteins affect gamma delta T cell development and how gamma delta T cells, and in particular of IL-17A-producing gamma delta T cells, contribute to inflammatory skin diseases such as allergic contact dermatitis, psoriasis, and atopic dermatitis.