(A) HLA alleles of patient receiving a double cord blood transplantation and of the 2 CBU infused. Patient and CBU1 present 2 mismatches in HLA-A and HLA-B loci; the mismatches at these loci occur in the HvG (HLA-A*03:01) and GvH (B*44:02) vectors, respectively, because the patient and donor are homozygous at these loci. CBU2 and the patient present only one mismatch (only in the HvG vector; A*32:01). These units present single mismatches in HLA-A in the HvG vector (A*03:01 in CBU1 and A*32:01 CBU2). (B) Evaluation of anti-HLA antibodies in the patient's serum. The patient's serum shows strong reactivity against the antigen preparation of A*32:01 present in CBU 2 and shows negligible reactivity against A*03:01 present in CBU1 and the patient's self–HLA-A antigen A*02:01. These test results indicate that CBU2 is at high risk of rejection and CBU1 is likely to engraft. Professional illustration by Paulette Dennis.