Flip the coin: IL-7 and IL-7R in health and disease

Copyright © 2019, The Author(s), under exclusive licence to Springer Nature America, Inc.The cytokine IL-7 and its receptor, IL-7R, are critical for T cell and, in the mouse, B cell development, as well as differentiation and survival of naive T cells, and generation and maintenance of memory T cells. They are also required for innate lymphoid cell (ILC) development and maintenance, and consequently for generation of lymphoid structures and barrier defense. Here we discuss the central role of IL-7 and IL-7R in the lymphoid system and highlight the impact of their deregulation, placing a particular emphasis on their 'dark side' as promoters of cancer development. We also explore therapeutic implications and opportunities associated with either positive or negative modulation of the IL-7-IL-7R signaling axis.J.T.B. is funded by the consolidator grant ERC CoG-648455 from the European Research Council, under the European Union’s Horizon 2020 research and innovation programme, and the FAPESP/20015/2014 and PTDC/MEC-HEM/31588/2017 grants from Fundação para a Ciência e a Tecnologia, Portugal; S.K.D. is funded by the intramural program of the US National Cancer Institute, National Institutes of Health, and the Children’s Cancer Foundation; B.S. is funded by the MRC (United Kingdom) under U117573801 and MR/P011225/1.