- DONOR: Related donor who is human leukocyte antigen (HLA) genotypically identical at least at one haplotype and may be genotypically or phenotypically identical for serological typing for HLA-A, B, C, and at the allele level for DRB1 and DQB1; related donors other than siblings must be matched at HLA-A, B, and C (at highest resolution available at the time of donor selection) and at DRB1 and DQB1 by deoxyribonucleic acid (DNA) typing; if more than one HLA-identical sibling is available, priority will be given to the oldest normal donor