The development of IL-17/IFN-γ-double producing CTLs from Tc17 cells is driven by epigenetic suppression of Socs3 gene promoter

The plasticity of T lymphocytes induced by epigenetic modifications of gene promoters may play a pivotal role in controlling their effector functions, which are sometimes causally associated with immune disorders. IL -17-producing T cells, which induce type 17 immune responses, are newly identified pathogenic effector cells. The type 1 signature cytokine IFN-? strongly inhibits their differentiation, indicating a mutually exclusive relationship between type 17- and type 1-immune responses. However, many reports indicate the presence of a unique IL-17/IFN-?-double producing T-cell subset in various inflammatory settings, although the mechanisms responsible for their development and their precise functions remain unclear. Here, we demonstrate that IL-12 permits the conversion of mouse IL-17-producing CD8+ T (Tc17) cells to IL-17/IFN-?-double producing CD8+ T (Tc17/IFN-?) cells, and that this conversion is due to repressive epigenetic modifications of Socs3 gene promoters. Moreover, we show that SOCS3 strongly regulates the capability of Tc17 cells to produce IL-17, in addition to regulating the expression of the type 17-master regulator ROR?t. These findings elucidate the mechanisms underlying the conversion of Tc17 cells into Tc17/IFN-? cells. As these cells are known to have potent antitumor activities, manipulation of these conversion mechanisms for therapeutic tumor immunity may be possible.