Cutting edge: IL-27 is a potent inducer of IL-10 but not FoxP3 in murine T cells.

The cytokine IL-27 is important for restricting inflammation in response to a wide variety of immune challenges. In this study, we demonstrate that IL-27 induces expression of the anti-inflammatory cytokine IL-10 by CD4+ and CD8+ T cells. IL-27 relied upon the Th1 transcription factor STAT1 to induce IL-10+IFN-gamma+FoxP3- Th1 cells, which were recently shown to be key negative regulators during certain infections. Il27ra-/- mice generated fewer IL-10+ T cells during both Listeria monocytogenes infection and experimental autoimmune encephalomyelitis. The data presented here indicate a novel mechanism for the induction of IL-10 expression by T cells and provide a mechanistic basis for the suppressive effects of IL-27.