An overview of IL-17 function and signaling

Since the discovery of interferons over 50 years ago, efforts to understand the biochemistry, molecular biology and biological activities of cytokines have been intense and rewarding. Although there are several hundred cytokines and receptors currently recognized, they in fact fall into a fairly limited set of subfamilies (reviewed in [1,2]). Within these families (and in some cases even outside them), cytokines share many structural and functional features that have provided a framework for understanding their biological activities and signal transduction mechanisms. This review will focus on interleukin (IL)-17, the founding member of the newest subclass of cytokines, which has received considerable attention in the last several years due to its central role in the Th17 system. 2. IL-17 and its receptor The gene encoding IL-17 was discovered in 1993 in a rodent T cell library by subtractive hybridization. Then termed CTLA-8, IL-17 was recognized to have homology to an open reading frame encoded within a T cell-tropic γ-herpesvirus, Herpesvirus Saimiri [3], but did not resemble any known cytokines. The significance of the viral homology is still unclear. Nonetheless, the distinct sequence nature of IL-17 relative to other cytokine families wa