GSE159031
IL-22-dependent dysbiosis and mononuclear phagocyte depletion contribute to steroid-resistant gut graft-versus-host disease in mice I
CD4+ and CD8+ T cells can reciprocally differentiate into Th/Tc1, Th/Tc17 and Th/Tc22. Although alloreactive Th/Tc1 cells play a critical role in initiating pathogenesis of gut acute graft-versus-host disease (Gut-aGVHD), the pathogenic T cells in steroid-resistant Gut-aGVHD (SR-Gut-aGVHD) remains unclear. Here, we show that in murine models of SR-Gut-aGVHD, the pathogenesis is associated with reduction of IFN-g+ Th/Tc1 and IL-17A+IL-22- Th/Tc17 but expansion of IL-17-IL-22+ Th/Tc22, particularly Tc22 cells. IL-22 from Th/Tc22 cells causes dysbiosis. Using a Gut-aGVHD model induced by alloreactive IFN-g-/- CD8+ T cells, we show that the Gut-aGVHD pathogenesis requires both dysbiosis and depletion of CX3CR1hi mononuclear phagocytes (MNP) that regulate intestinal bacterial translocation. Absence of IFN-g leads to preferential expansion of Tc22 that induce dysbiosis by augmenting RegIIIg production, and depletion of CX3CR1hi MNP via its PD-1 interaction with tissue PD-L1. Interestingly, SR-Gut-aGVHD is also associated with depletion of CX3CR1hi MNP that reduces expansion of Tc22 under steroid treatment. Our studies indicate that expansion of Th/Tc22, dysbiosis, and depletion of CX3CR1hi MNP cells play critical roles in SR-Gut-aGVHD pathogenesis. These results provide new avenue towards studies in patients and call for caution in clinical testing of IL-22 agonists or IFN-g antagonist in patients. Overall design: Experiments of the relationship between the SR-Gut-aGVHD pathogenesis and the regulation of IFN-?+ Th/Tc1, IL-17A+IL-22- Th/Tc17 and IL-17-IL22+Th/Tc22 cells.