Human leukocyte antigen matching in cord blood transplantation

Cord blood transplants are now widely used for allogeneic hematopoietic stem cell transplants (HSCT) in patients with various hematologic disorders. One advantage of this source of stem cells is the decrease of graft-versus-host disease (GVHD) because of the immaturity of lymphocytes at birth. The role of human leukocyte antigen (HLA) for donor search and post-transplant outcomes is not very well described. The Eurocord Registry has analyzed more than 1,000 cases of unrelated cord blood transplants (UCBT). Results show that HLA matching is important for engraftment and graft versus leukemia but not for survival and GVHD. Allelic matching for HLA-A, -B, -C, -DRB1, and -DQB1 shows that the number of mismatches is very high and does not allow identification of prognostic factors. Contrary to the criteria of donor choice for an unrelated bone marrow transplant where HLA allelic matching is important, in the case of cord blood transplants the number of nucleated cells infused is the most important predictor of success.