HLA-A and acute graft versus host disease: Interestingly, for other HLA class-I mismatches (HLA-A and -B) both low-resolution level (antigenic) as well as high-resolution level (allelic) mismatches are associated with an increased risk of acute GVHD; whereas for HLA-C mismatches this increased risk is only observed for HLA-C antigenic mismatches (9, 12).