Notch2 with retinoic acid license IL-23 expression by intestinal EpCAM⁺ DCIR2⁺ cDC2s in mice

Despite the importance of IL-23 in mucosal host defense and disease pathogenesis, the mechanisms regulating the development of IL-23-producing mononuclear phagocytes remain poorly understood. Here, we employed an Il23a(Venus) reporter strain to investigate the developmental identity and functional regulation of IL-23-producing cells. We showed that flagellin stimulation or Citrobacter rodentium infection led to robust induction of IL-23-producing EpCAM(+) DCIR2(+) CD103(-) cDC2s, termed cDC(IL23,) which was confined to gut-associated lymphoid tissues, including the mesenteric lymph nodes, cryptopatches, and isolated lymphoid follicles. Furthermore, we demonstrated that Notch2 signaling was crucial for the development of EpCAM(+) DCIR2(+) cDC2s, and the combination of Notch2 signaling with retinoic acid signaling controlled their terminal differentiation into cDC(IL23), supporting a two-step model for the development of gut cDC(IL23). Our findings provide fundamental insights into the developmental pathways and cellular dynamics of IL-23-producing cDC2s at steady state and during pathogen infection.