Early studies that first linked histone acetylation with GVHD revealed that the panoramic HDAC inhibitor (pan-HDACi) suberoylanilide hydroxamic acid (SAHA) ameliorate and delayed the development of GVHD and reduced the serum level of proinflammatory cytokines such as IFN-γ and TNF-α following allogeneic bone marrow transplantation (157, 158). Here, HDAC9 is linked to graft versus host disease.