Ex vivo activation of naturally occurring IL-17-producing T cells does not require IL-6.

Interleukin (IL-)17 is a potent proinflammatory cytokine for which an important role in the immune response against infections and in autoimmune diseases has been demonstrated. Recently, it has been shown that - in addition to mature T cells which are primed in the immune periphery - this cytokine can also be produced by T cells in the thymus, so-called naturally occurring IL-17-producing T cells (nT17 cells). In this study we demonstrate that the generation and activation of nT17 cells in the thymus do not depend on the cytokine IL-6. In addition, nT17 cells are not regulated by IL-2. These properties of nT17 cells significantly differ from induced IL-17-producing T cells primed in the immune periphery (iT17 cells). Given the strong association of IL-17-producing T cells with immune responses against infections and human autoimmune diseases, closer characterization of nT17 cells is warranted.