A clinician's guide to HLA matching in allogeneic hematopoietic stem cell transplant

Human leukocyte antigen (HLA) matching is an essential component of allogeneic hematopoietic stem cell transplant (HSCT). However, for some clinicians the biology underpinning HLA structure and function may be but a distant memory from lectures many years past, and, understanding the complexities of HLA matching can be challenging for clinicians new to the field, particularly as there have been several important advances in the field this past decade. In this review, we provide an up to date resource to educate and remind clinicians of: 1) Why HLA matching matters, including reviewing the role HLA molecules play in the adaptive immune system and the consequences of HLA mismatch. 2) What is involved in HLA matching, including a review of the different HLA genes, HLA protein structure, HLA sequencing approaches through time, and HLA allele nomenclature. And 3) how to apply this knowledge to identify an HLA matched donor for allogeneic HSCT, including discussion regarding HLA-DPB1 permissive mismatching and Donor Specific Antibodies.