aGVHD. Simplified sketch showing the mode of action of multiple immunosuppressive strategies that were all developed from animal models into a clinical application for aGVHD. Ab, antibody; ECP, extracorporal photophoresis; ITAM, immunoreceptor tyrosine-based activation motif; MMF, mycophenolate mofetil; MSC, mesenchymal stroma cells; mTOR, mammalian target of rapamycin complex; NKT, natural killer T cells.