Interestingly, GVHD inhibition was achieved by administering the TLR7/8 agonist before BM transplantation, in contrast to the GVHD acceleration with post-BM transplantation TLR agonist administration, with the latter likely caused by the release of overwhelming pro-inflammatory cytokines with inadequate control by IDO [46]. This evidence concerns the gene TLR7 and graft versus host disease.