 Several groups have identified ways to induce IL-17 production both "in vitro" and "in vivo" by distinct cytokines, called TGF-β and IL-6, without the need for IL-23.Although IL-23 is not required for IL-17 expression in this situation, IL-23 may play a role in promoting survival and/or proliferation of the IL-17 producing T-cells.Recently, Ivanov "et al."