These results indicate that Mito-STAT3 deficiency in donor CD4+ and CD8+ T cells increases Mito-ROS production and Mito dysfunction, but does not cause significant inhibition of GSH/Myc pathways or dysfunction of metabolic reprogramming of alloactivated T cells, such that these donor T cells have no impairment of their ability to induce acute GVHD. The gene discussed is CD4; the disease is acute graft versus host disease.