2010-04-27
The human leukocyte antigens (HLA)
system is the major histocompatibility complex (MHC) in humans. These proteins
are encoded by a large set of genes (alleles) and are essential elements for
immune function. Thus, they play an important role in the success of solid
organ and hematopoietic progenitor cell transplantation. When HLA nomenclature
was adopted in 1987, it was thought that the naming convention put in place
could accommodate all of the HLA alleles likely to be sequenced. Since then,
new additions to the original code have been added to extend the use of the
nomenclature system.
As the science of HLA matching has
advanced and more and more allelic variation discovered, the capacity to name
newly discovered alleles by the current HLA naming convention has been
exceeded. As a result, a new version of HLA nomenclature was launched on April
1, 2010. The World Marrow Donor Association (WMDA) and National Marrow Donor
Program (NMDP) are working with organizations and suppliers from around the
world to ensure that worldwide systems are prepared for the new version of HLA
nomenclature.
The current convention has been
revised in three ways. First, with the ever increasing number of HLA alleles,
it has been decided to introduce colons (:) into the allele names to act as
delimiters of the separate fields. It will be mandatory to include the leading
zeros currently included in the alleles; this will help to lessen any confusion
in the conversion to the new style of nomenclature, but no further leading
zeros will be added to allele names.
Second, the “w” has been removed from
the HLA-C allele names, but will be retained in the HLA-C antigens’ names, to
avoid confusion with the factors of the complement system and epitopes on the
HLA-C molecule often termed C1 and C2 that act as ligands for the killer-cell
immunoglobulin-like receptors.
Lastly, the level of resolution
achieved by many of the HLA-typing technologies employed today does not always
allow for a single HLA allele to be unambiguously assigned. For some purposes,
it is helpful to provide codes that aid the reporting of certain ambiguous
alleles “strings.” To this end, codes have been introduced to allow for the
easy reporting of both HLA alleles that encode for identical peptide-binding
domains and HLA alleles that share identical nucleotide sequences for the exons
encoding the peptide binding domains.
Lists of old and new allele names will be made
available through the IMGT/ HLA Database (www.ebi.ac.uk/imgt/hla). HLA
allele code information is available at http://bioinformatics.nmdp.org/HLA/Ver3_Nomenclature_Allele_Codes.
For general information about this transition, visit www.marrow.org/hla.
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