Previous association studies focusing on MHC region SNPs have suggested that the success of unrelated HSCT might be influenced by non-HLA genetic variation within the MHC, for example Petersdorf et al [38] identified two SNPs as markers for disease-free survival and acute GVHD, one of which is a putative expression quantitative locus for MICA and MICB genes. Here, MICB is linked to acute graft versus host disease.