Macrophages acquire distinct phenotypes during tissue stress and inflammatory responses.Macrophages are roughly categorized into two different subsets named inflammatory M1 and anti-inflammatory M2 macrophages.We herein identified a unique pathogenic macrophage subpopulation driven by IL-23 with a distinct gene expression profile including defined types of cytokines.The freshly isolated resting mouse peritoneal macrophages were stimulated with different cytokines in vitro,the expression of cytokines and chemokines were detected by microarray,real-time PCR,ELISA and multiple colors flow cytometry.Adoptive transfer of macrophages and imiquimod-induced psoriasis mice were used.In contrast to M1-and M2-polarized macrophages,IL-23-treated macrophages produce large amounts of IL-17A,IL-22 and IFN-y.Biochemical and molecular studies showed that IL-23 induces IL-17A expression in macrophages through the signal transducer and activator of transcription 3 (STAT3)-retinoid related orphan receptor-γ T (RORγT) pathway.T-bet mediates the IFN-y production in IL-23-treated macrophages.Importantly,IL-23-treated macrophages significantly promote the dermatitis pathogenesis in a psoriasis-like mouse model.IL-23-treated resting macrophages express a distinctive gene expression prolife compared with M1 and M2 macrophages.The identification of IL-23-induced macrophage polarization may help us to understand the contribution of macrophage subpopulation in Th17-cytokines-related pathogenesis.