Dendritic cells (DCs) are essential APCs and play a crucial role in initiating and regulating the adaptive immune response. In this study, we have reported that P2Y6, a member of G protein-coupled receptors, inhibits the maturation and activation of DCs via suppressing the activation of the transcription factor NF-?B. Furthermore, loss of P2Y6 does not impact T cells homeostasis in the steady-state. However, in vitro studies show that P2Y6 signaling inhibits the production of IL-12 and IL-23 and the polarization of Th1 and Th17 subsets mediated by DCs. In addition, we find that mice lacking P2Y6 develop more severe experimental autoimmune encephalomyelitis compared with wild-type mice. Our results indicate that P2Y6 functions as a pivotal regulator on DC maturation, and the loss of P2Y6 results in the aggravated experimental autoimmune encephalomyelitis, which suggests that P2Y6 may play a pivotal role in the pathogenesis of autoimmune diseases. Copyright 2020 by The American Association of Immunologists, Inc.