Therefore, IFN-γR signaling is emerging as an attractive target (15–17) for graft-versus-host disease (GVHD) intervention, as corroborated by clinical results using the nonselective JAK1/2 inhibitor ruxolitinib (Rux) and preclinical results with barcitinib (18, 19). The gene discussed is JAK1; the disease is graft versus host disease.