Harnessing the biology of IL-7 for therapeutic application

Interleukin-7 (IL-7) induces T cell proliferation and enhances antigen-specific immune responses: attributes that pinpoint its value as a potential therapeutic agent. This Review summarizes preclinical and clinical data on the immunorestorative effects of IL-7 in various pathologies and discusses the conditions for which IL-7 therapy might be of use. Interleukin-7 (IL-7) is required for T cell development and for maintaining and restoring homeostasis of mature T cells. IL-7 is a limiting resource under normal conditions, but it accumulates during lymphopaenia, leading to increased T cell proliferation. The administration of recombinant human IL-7 to normal or lymphopenic mice, non-human primates and humans results in widespread T cell proliferation, increased T cell numbers, modulation of peripheral T cell subsets and increased T cell receptor repertoire diversity. These effects raise the prospect that IL-7 could mediate therapeutic benefits in several clinical settings. This Review summarizes the biology of IL-7 and the results of its clinical use that are available so far to provide a perspective on the opportunities for clinical application of this cytokine.