Development, phenotype and function of a distinct macrophage subpopulation induced by IL-23

Macrophages acquire distinct phenotypes during tissue stress and inflammatory responses. Classically, macrophages are categorized into two different subsets named inflammatory M1 and anti-inflammatory M2 macrophages. We herein identified a unique pathogenic macrophage subpopulation, named M17, driven by IL-23 with a distinct gene expression profile including cytokines and membrane molecules. In contrast to M1 and M2-polarized macrophages, M17 macrophages express high levels of CXCR5 on the cell surface and produce large amounts of IL-17A, IL-22 and IFN-γ. 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, while induces IFN-γ through T-bet. Importantly, IL-23-induced M17 macrophage polarization promotes the pathogenesis of psoriasis in vivo. The characteristics and significances of M17 macrophage subpopulation in the physiological status and pathogenesis caused by infections, tumors and graft rejection needs to be explored. To further demonstrate whether M17 macrophage polarization represents a distinct polarization of macrophages, we detected gene expression profiles of M1, M2 and M17 polarized macrophages by microarray methods.