Duality in the Th17-Treg developmental decision

Each of the effector CD4 T-cell lineages - Th1, Th2, and the more recently identified Th17 - arises from pluripotent naïve precursors whose developmental fate is largely controlled by cytokines that act in concert with antigenic signals. Remarkably, development of the Th17 lineage has been linked to that of regulatory T cells, which obviate or downregulate Th17 responses to preserve immune homeostasis, through a shared requirement for the cytokine transforming growth factor-beta. Several new studies offer insights into the mechanism whereby the precursors of these subsets are directed into distinct lineages.