Regulation of Th17 maturation by interleukin 4.

Regulation of immune responses and control of autoimmunity depend on layers of checkpoints, cell-cell interactions, and soluble mediators, both during lymphocyte development and in the course of immune responses. With the definition and study of multiple distinct T-cell subsets, it is now apparent that, while specialized regulatory T cells (Tregs) have essential roles in immune homeostasis, important regulatory interactions also occur between the known effector Th subsets such as Th1, Th2 and Th17. In this review, we discuss the regulatory effects of the Th2 cell cytokine interleukin 4 (IL-4) on Th17 cell function, and we highlight emerging data, which indicate the importance of this interaction in both animal model systems and human disease.