In a recent paper, Morishima et al., analyzing 7898 Japanese pairs transplanted from a matched unrelated donor (MUD) characterized by a complete HLA allele typing data, showed a significant relative risk in HLA allele mismatch, compared with match at HLA-A, -B, -C, and -DPB1 loci, for grade III-IV GvHD, and HLA-C for chronic GvHD. Here, HLA-A is linked to graft versus host disease.