CD4 and graft versus host disease: In agreement, OX40 blockade using the antagonizing mAb amlitelimab significantly extended graft-versus-host disease (GvHD)-free survival and delayed clinical signs of acute GvHD in a nonhuman primate model by restraining CD4 T cell expansion and preserving Treg reconstitution following hematopoietic stem cell transplantation (Tkachev et al., 2017).