Successful engraftment after cord blood transplantation from an HLA‐homozygous donor (homo‐to‐hetero cord blood transplantation) in a primary myelofibrosis patient with broad HLA antibodies

BACKGROUND: Donor-specific human leukocyte antigen (HLA) antibodies are a significant risk factor for graft failure in cord blood transplantation (CBT). Although there are several treatments to decrease HLA antibodies, such as platelet transfusion, plasma exchange, rituximab, and bortezomib, their effectiveness has not been established. STUDY DESIGN AND METHODS: We herein report the case of a primary myelofibrosis (PMF) patient with broad HLA antibodies who underwent CBT from an HLA-homozygous donor in which the alleles were matched only in the host-versus-graft direction (homo-to-hetero CBT). RESULTS: The cord blood was killer cell immunoglobulin-like receptor (KIR) ligand matched. She received a reduced-intensity conditioning regimen. We used tacrolimus and mycophenolate mofetil as prophylaxis against graft-versus-host disease (GVHD). The neutrophils engrafted on Day 31. A chimerism analysis with fluorescence in situ hybridization of peripheral blood cells showed 99.9% donor type on Day 33. She developed only mild acute skin GVHD and chronic skin GVHD. CONCLUSION: This case indicates the usefulness of homo-to-hetero CBT in a patient with broad HLA antibodies with a strong mean fluorescence intensity, which is a significant risk factor for graft failure. Further studies are necessary to determine the risk of GVHD and to elucidate the association between KIR ligand incompatibility and graft failure in homo-to-hetero CBT.