In a clinical study, a 9-year-old child with acute lymphoblastic leukemia (ALL) that had received allo-transplantation, with an HLA-A HLA-B, HLA-DRβ1 identical and unrelated female donor, developed grade IV aGvHD at day 70 post-transplant. The gene discussed is HLA-B; the disease is acute lymphoblastic leukemia.