Study cohort. Patients with hematological malignancies who received their first allogeneic HSCT with MUDs between 2005 and 2014 were included (n = 1505). Patients eligible for this study had donor and recipient HLA typing performed at the HLA-A, HLA-B, HLA-C and HLA-DRB1, HLA-DRB3/4/5, HLA-DQB1, and HLA-DPB1 loci using sequenced-based typing methods at high-resolution levels. Patients with second allogeneic HSCT, diagnosis of aplastic anemia and solid tumors, age younger than 18 years, and those who did not receive ATG for GVHD prophylaxis were excluded from the analysis. Therefore, the final study cohort included 1004 patients transplanted with 8/8 MUDs at HLA-A, HLA-B, HLA-C, and HLA-DRB1.