HLA matching in pediatric stem cell transplantation

For several malignant and nonmalignant disorders such as leukemias, lymphomas, or inborn errors of hematopoiesis, stem cell transplantation is the only curative option. Depending on the underlying cause of the disease, the conditioning regimens, source of the stem cells, and graft composition may vary. Possible stem cell donors are selected from databases considering existing major histocompatibility genes of the donor and the recipient. This is currently performed by matching human leukocyte antigen (HLA)-A, -B, and -C for class I, as well as HLA-DRB1 and -DQB1 for class II. Stem cell transplantation for nonmalignant disorders is a specialty of pediatrics. While algorithms for donor selection in these cases are generally similar, the objective of optimizing a possible graft-versus-leukemia effect is less important. In this article, we aim to provide an overview on the current methods for HLA typing and the algorithms for HLA matching. We also address ethical aspects regarding children and minors as stem cell donors.