CD4 and graft versus host disease: Alloantigen-specific CD4+ Tregs administered to NSG mice infused with xenogeneic PBMCs have been shown to efficiently delay clinical signs of GVHD and skin transplantation, while natural CD4+ Tregs or polyclonally expanded are much less efficient (74, 75) and antigen-specific CD8+ Tregs generated by either expansion with donor antigens or generation of CAR-CD8+ Tregs represent a promising future.