TNFRSF9 and graft versus host disease: In addition, a mouse study to investigate the effect of donor-derived CD19 CAR-T cells in allogeneic HSCT showed that allogeneic CAR-T cells exert potent graft-versus-lymphoma activity and decreased GvHD and identified that TNFRSF9 co-stimulated CAR-T cells increased the occurrence of GvHD [49] even though TNFRSF9 co-stimulation has been known to decrease T cell exhaustion by repetitive CAR signaling [50,51].