IL-13-producing Th1 and Th17 cells characterize adaptive responses to both self and foreign antigens.

In helper T cells, IL-13 is traditionally considered a Th2-type cytokine that is coexpressed with IL-4. Using mouse models of immunization and autoimmunity, we demonstrate that IL-13 is frequently uncoupled from IL-4, and that it can be produced by both IFN-γ(+) Th1 cells and IL-17(+) Th17 cells. We report that these IL-13-producing Th1 and Th17 cells are distinct from classical IL-4(+) Th2 cells and that they are relatively common, appearing in the context of both protective and pathogenic T-cell responses. We also demonstrate that IL-13 and Th2-type cytokines can have important consequences in Th1- and Th17-dominated settings, such as lymphopenia-induced autoimmune disease, where they can be either pro- or anti-inflammatory, depending on whether they act on innate or adaptive immune cells. Taken together, our studies indicate that IL-13 production is more widespread than previously appreciated and that blocking this cytokine may have therapeutic benefits even in settings where traditional IL-4-driven Th2-type responses are not evident.