PDCD1 and graft versus host disease: In contrast, we observed that PD-1 signaling in STAT3–/– T cells reduced both Glyco-ATP (glycolysis) and Mito-ATP (FAO) and also reduced GSH synthesis, with reduced expression of CD36 and CD98 to a degree that induced metabolic dysfunction and deletion of T cells infiltrating the liver and gut, thereby preventing GVHD.