Abstract
IL-27, as a pleiotropic cytokine, promotes the differentiation of naïve T cells to Th1, while suppressing Th2 and Th17 differentiation in the periphery. However, the role of IL-27 in the thymocyte development remains unknown. Here we showed that IL-27 was highly expressed in thymic plasmacytoid dendritic cells (pDCs) while its receptor expression was mainly detected in CD4(+) single-positive (SP) thymocytes. Deletion of the p28 subunit in DCs resulted in a reduction of the most mature Qa-2(+) subsets of CD4(+) SP T cells. This defect was rescued by intrathymic administration of exogenous IL-27. In vitro differentiation assay further demonstrated that IL-27 alone was able to drive the maturation of the newly generated 6C10(+)CD69(+)CD4(+) SP cells into Qa-2(+) cells. Collectively, this study has revealed an important role of thymic DCs-derived IL-27 in the regulation of the phenotypic maturation of CD4(+) SP thymocytes.