IL-17+ γδ T cells as kick-starters of inflammation

Shortly after the discovery of interleukin 17 (IL-17)-producing CD4(+) helper T cells (T(H)17 cells), it was found that gamma delta T cells can also secrete large amounts of this pro-inflammatory cytokine. A decade later, it is now known that IL-17(+) gamma delta T cells (gamma delta 17 T cells) are often the main providers of IL-17A in various models of inflammatory diseases, while they also contribute to protective immune responses to infectious organisms. Due to an intricate thymic program of differentiation, gamma delta 17 T cells are able to respond faster than T(H)17 cells do and thus predominate in the early stages of inflammatory responses. Here we review the current knowledge of the development, activation and pathophysiological functions of gamma delta 17 T cells, aiming to increase the awareness in the community of the therapeutic potential of this 'other side' of IL-17-mediated immune responses.