• Human leukocyte antigen (HLA) nomenclature began by assigning each locus consecutive numbers corresponding to new anti-HLA antibodies discovered (HLA-A1, -A2, etc).
• It was realized early on that some anti-HLA antibodies recognized multiple HLAs, hence the need to “split” what was formerly thought to be a single antigen into newly discovered subtypes, that is, B16 → B38, B39; B17 → B57, B58.
• With the advent of genetics, HLA loci were discovered to be much more polymorphic than could ever be classified by serology. For example, at the genetic level, HLA-B57 appeared to be a collection of alleles B*57:01, B*57:02, etc.
• In this nomenclature convention (i.e., B*57:01), the first two numbers represent the serologically defined antigen and the second two represent the allelic subtype.
• Finally, in 2011 a new nomenclature was introduced to address the problem that arises at loci that have more than 99 genetically defined alleles – that is, HLA-B*5799 would be the last allele in which the genetic resolution can be described by two digits. The newest nomenclature looks like HLA-B*57:01:02, and the last two digits define alleles of B*57:01 with silent mutations.
• Patients with long allograft survival times may have typing results in their charts and medical records conforming to outdated nomenclatures.
Holdsworth R, Hurley CK, Marsh SGE, et al:
The HLA dictionary 2008: a summary of HLA-A, -B, -C, -DRB1/3/4/5, and -DQB1 alleles and their association with serologically defined HLA-A, -B, -C, -DR, and -DQ antigens. Tissue Antigens 2009;72:95-170.
Tait BD:
The ever-expanding list of HLA alleles: changing HLA nomenclature and its relevance to clinical transplantation. Transplant Rev (Orlando) 2011;25:1-8.
