Interleukin 27 (IL-27) was first characterized as a proinflammatory cytokine with T helper type 1-inducing activity. However, subsequent work has demonstrated that mice deficient in IL-27 receptor (IL-27R alpha) show exacerbated inflammatory responses to a variety of challenges, suggesting that IL-27 has important immunoregulatory functions in vivo. Here we demonstrate that IL-27R alpha-deficient mice were hypersusceptible to experimental autoimmune encephalomyelitis and generated more IL-17-producing T helper cells. IL-27 acted directly on effector T cells to suppress the development of IL-17-producing T helper cells mediated by IL-6 and transforming growth factor-beta. This suppressive activity was dependent on the transcription factor STAT1 and was independent of interferon-gamma. Finally, IL-27 suppressed IL-6-mediated T cell proliferation. These data provide a mechanistic explanation for the IL-27-mediated immune suppression noted in several in vivo models of inflammation.
Batten, M., Li, J., Yi, S., Kljavin, N. M., Danilenko, D. M., Lucas, S., Lee, J., de Sauvage, F. J., & Ghilardi, N. (2006). Interleukin 27 limits autoimmune encephalomyelitis by suppressing the development of interleukin 17-producing T cells. Nature Immunology, 7(9), 929-936. https://doi.org/10.1038/ni1375 (Original work published 2006)