confirmed that IL-23R alpha was required for the induction of GVHD development and that absence of IL-23R signaling in both CD4+ and CD8+ T cells resulted in a decrease in the production of GM-CSF and IFN-γ in the GI tract, further corroborating the importance of IL-23 signaling during acute GVHD (53). Here, CD4 is linked to graft versus host disease.