Deciphering the role of γδ T cells in skin inflammatory diseases: Insights from psoriasis, atopic dermatitis, and alopecia areata.

Gamma delta (γδ) T lymphocytes are a heterogeneous population of immune cells that correspond between 1 % and 5 % of mice lymphoid tissues and human blood lymphocytes. However, their prevalence increases markedly in epithelial and mucosal tissues such as the skin. The ability of γδ T cells to rapidly produce cytokines positions them as key contributors in the early stages of immune response. For this reason, γδ T cells bridge innate and adaptive immunity, thus regulating early stages of inflammatory processes, wound healing, and defence against pathogens and tumours. Remarkably, γδ T cells are also involved in the pathogenesis of skin autoimmune diseases such as psoriasis, atopic dermatitis and alopecia areata. This chapter addresses the involvement of several γδ T cell subsets in these inflammatory skin diseases, focusing on their ontogeny and functional phenotypes, in both mouse and human skin.