T-cell cultures differentiated in the presence of G-1 secreted threefold more IL-10, with no change in IL-17A, tumour necrosis factor-α, or interferon-γ. Moreover, inhibition of extracellular signal-regulated kinase (but not p38 or Jun N-terminal

kinase) signalling blocked the response, while analysis of Foxp3 and RORγt expression demonstrated increased numbers of IL-10+ cells in both the Th17 (RORγt+) and Foxp3+ RORγt+ hybrid T-cell compartments. Our findings translated in vivo as systemic treatment of male mice with G-1 led to increased IL-10 secretion from splenocytes following T-cell receptor cross-linking. These results demonstrate that G-1 acts directly on CD4+ T cells, and to our knowledge provide the first example of a synthetic small molecule capable of eliciting IL-10 expression in Th17 or hybrid T-cell populations. CD4+ helper T lymphocytes orchestrate adaptive immune responses to invading Metabolism inhibitor pathogens, and are critical to the pathogenesis Veliparib research buy of numerous disease processes, including autoimmunity and cancer. They are an attractive drug target because of their central role in immunity, and their implication in a wide variety of diseases. There are

several distinct lineages of CD4+ helper T cells, each specialized in enhancing specific branches of the immune system. The original paradigm described by Mossman and Coffmann1 divided Orotic acid CD4+ helper T lymphocytes into the T helper type 1 (Th1) and Th2 populations, with Th1 cells producing interferon-γ (IFN-γ) and coordinating

cellular immunity responses and Th2 cells secreting humoral immunity mediators such as interleukin-4 (IL-4), IL-5 and IL-13. In 2005, the Th1–Th2 paradigm was expanded as the Th17 population emerged as a third class of helper/effector T cell. Th17 cells are characterized by expression of the transcription factor RORγt,2,3 and secrete pro-inflammatory cytokines including IL-214 and IL-17A/F. These cells are important to controlling infections by extracellular pathogens, but also appear to play a deleterious role in human health by contributing to the pathogenesis of numerous autoimmune diseases.5 In mice, Th17 differentiation depends on transforming growth factor-β (TGF-β) and IL-6- or IL-21-mediated signal transducer and activator of transcription 3 (STAT3) activation,5 while IL-23 signalling plays a critical role in stabilizing the Th17 phenotype.6 Although Th1, Th2 and Th17 effector T cells coordinate a robust and diverse arsenal of adaptive immune responses necessary for the maintenance of human health, mechanisms of restraint must limit effector responses to protect the host from immune-mediated damage. A major breakthrough in elucidating the mechanisms of adaptive immune regulation emerged with the identification of an array of regulatory T (Treg) -cell populations.