Development and function of interleukin 17-producing γδ T cells

Interleukin (IL) 17 is a phylogenetically ancient cytokine that has been adopted by the adaptive immune system, and the investigation of adaptive T helper (Th) 17 cells has substantially contributed to our understanding of the molecular requirements for the induction, regulation, and function of IL-17. However, IL-17 is in fact produced by a large variety of innate immune cells and exerts its most significant biological functions at the interface of the organism with its environment, such as, for example, at epithelial surfaces, where gamma delta T cells are a prominent source of IL-17. In this review, we will give an overview on the concepts of commitment of gamma delta T cells to effector phenotypes, focusing on IL-17-producing gamma delta T cells (gamma delta T17 cells). The role of gamma delta T17 cells in animal models of autoimmunity will be discussed as well as the prerequisites for the development of human gamma delta T17 cells and their potential importance for human disease conditions.