Nomenclature for Factors of the HLA System, 2026

The WHO Nomenclature Committee for Factors of the HLA System has met several times since the publication of the last major report in 2010.1 It met most recently in September 2023, to discuss additions to the serological defined HLA antigens. This report documents the additions and revisions to the nomenclature of HLA specificities following the principles established in previous reports.1-19 Links to these reports and details of HLA Nomenclature can be found on the website: hla.alleles.org The HLA-OLI pseudogene has been reported and officially named HLA-R. A full list of all recognised HLA genes is given in Table 1.20 Although at present it is only a recommendation that full-length sequences of the coding region of novel alleles be submitted, it was widely felt that in the future this should become a requirement for submission. Such requirement would remove many of the currently encountered ambiguities in the assignment of names to alleles for which partial sequences have been submitted and should not be burdensome as sequencing techniques have improved substantially since the submission conditions were first devised. In cases where novel mutations or polymorphisms are detected in non-coding regions of the gene, it will be a requirement that full-length sequences be submitted of both the novel allele and its most closely related allele. It should be noted with some caution that cells from which only partial sequences have been obtained may later be shown to have different or novel alleles when further sequencing is performed. This is of particular importance in cases where partial sequences of what appears to be the same allele have been obtained from several different cells. In such cases, all cells studied have been listed in this report. The list of those genes in the HLA region considered by the WHO Nomenclature Committee for Factors of the HLA System is given in Table 1. Current practice is that official designations will be promptly assigned to newly described alleles in periods between Nomenclature Committee meetings, provided that the submitted data and its accompanying description meet the criteria outlined above. A list of the newly reported alleles is published every three months in nomenclature updates in the journals HLA, Human Immunology and the International Journal of Immunogenetics. The listing of references to new sequences does not imply priority of publication. The use of numbers or names for alleles, genes or specificities which pre-empt assignment of official designations by the Nomenclature Committee is strongly discouraged. A total of 43,758 HLA alleles have been named as of December 2025. A complete listing of the numbers of alleles assigned for each HLA genes is given in Table 2. In September 2023, the WHO Nomenclature Committee for Factors of the HLA System met at the Stanford Blood Center located at Stanford University following the 18th International HLA and Immunogenetics Workshop held in Noordwijkerhout, the Netherlands in May 2022. The committee met to evaluate a proposal for the definition of additional and novel antigens defined in silico21. The in silico definition of HLA antigens was achieved by the systematic examination and cataloguing the amino acid (AA) replacements at specific residues determining epitopes (DEP) in all common HLA alleles at the classical HLA class I and class II loci Common and Well Documented (CWD2.0) for alleles of HLA-DRB3, -DRB4, -DRB5, -DQA1 and -DPA1 and Common, Intermediate and Well Documented (CIWD3.0) for alleles of HLA-A, -B, -C, -DRB1, -DQB1 and -DPB1.21-23 The committee voted to accept the proposed serologic nomenclature update provided that a validation study was conducted. The manuscript aiming to confirm these computationally predicted antigens defined by DEP residues for the 11 HLA loci was designed to assess and compare the antibody reactivity of patients' sera in solid phase assays with Single Antigen Bead (SAB) preparations from various HLA proteins24. The differences in correlation confirmed the distinctions between proposed associated antigens and identified a few additional antigens.21, 25 A full listing of all the serological specificities for HLA-A, -B, -C, -DR, -DQ, and -DP and cellular defined specificities for HLA-Dw and HLA-DPw are given in Table 3. The concept of an HLA Associated Antigen was introduced in 1991, with the understanding that serological types would be more closely associated with the allele sequence defining them. Thirteen associated antigens were named at this time: A203, A210, A2403, B703, B3901, B3902, B4005, B5102, B5103, B7801, DR103, DR1403, and DR1404.12 In 1996 the B2708 associated antigen was named and it was decided to shorten the B7801 antigen name to B78.15 Following the definition of novel associated antigens documented below, it has been necessary to update the names of four of these: A203, A210, B703, and DR103, have been updated to A0203, A0210, B0703, and DR0103. A full listing of all the Associated Antigens for HLA-A, -B, -C, −and -DR are given in Table 4. This report includes nomenclature for the serological specificities encoded by both the HLA-DQA1 and HLA-DQB1 genes. As such it is now possible to define a nomenclature for the paired combination of both subunits of HLA-DQ molecules. Table 5 lists those proteins encoded in cis by common DQ haplotype blocks. The specificities resulting from trans-encoded heterodimers should be presented in the same format. The newly assigned HLA antigens and associated antigens will be implemented in April 2026 and will be made available through the IPD-IMGT/HLA Database (www.ebi.ac.uk/ipd/imgt/hla) with the April 2026 release of the database.26-28 The IPD-IMGT/HLA Database continues to act as the official repository for HLA sequences named by the WHO Nomenclature Committee for Factors of the HLA System.26-28 The database contains sequences for all HLA alleles officially recognised by the WHO Nomenclature Committee for Factors of the HLA System and provides users with online tools and facilities for their retrieval and analysis. These include allele reports, alignment tools, and detailed descriptions of the source cells. The online IPD-IMGT/HLA Database submission tool allows both new and confirmatory sequences to be submitted directly to the WHO Nomenclature Committee. New releases of the database are made every three months, in January, April, July and October, with the latest version (release 3.63.0 January 2026) containing 43,758 HLA alleles. The database may be accessed via the worldwide web at www.ebi.ac.uk/ipd/imgt/hla. The IPD-IMGT/HLA Database is currently supported by the following organisations: NMDP, TxMiller Foundation, CareDx, DKMS, Gift of Life, Werfen, Scisco Genetics, the European Federation for Immunogenetics (EFI), GenDx, Pirche, ThermoFisher, the American Society for Histocompatibility and Immunogenetics (ASHI), LabCorp, Histogenetics, the Asia-Pacific Histocompatibility and Immunogenetics Association (APHIA), BAG Diagnostics, Protrans, Inno-train, and Anthony Nolan. The Committee would like to thank Dominic Barker, Michael Cooper, Sebastian Hopper and Surayia Akter for their work with the IPD-IMGT/HLA Database. Also thanked is Andy Yates and the staff at the European Bioinformatics Institute for their continued support of the IPD-IMGT/HLA Database. We would also like to thank the many organisations that provide financial support for the IPD-IMGT/HLA Database and Benjamin Hester of the ‘NMDP Foundation’ for his work in soliciting and coordinating the funding of this project. We are grateful to Stanford Blood Center for covering the cost for providing open access for this article. SGE Marsh, University College London, London, UK (Chairman) WF Bodmer, Oncology Department, Oxford University, Oxford, UK MN Carrington, Basic Science Program, Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA and Laboratory of Integrative Cancer Immunology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA & Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA HA Erlich, Benioff UCSF Children's Hospital Oakland Research Institute, Oakland, USA M Fernández-Viña, Stanford Blood Center, Palo Alto, USA & Department of Pathology, Stanford University School of Medicine, Stanford, USA S Heidt, Erasmus Medical Center, Rotterdam, & Leiden University Medical Center, Leiden, The Netherlands R Holdsworth, University of Melbourne, Melbourne, Australia WR Mayr, University of Vienna, Vienna, Austria M Maiers, Center for International Blood and Marrow Transplant Research, (CIBMTR), NMDP, Minneapolis, USA P Parham, Stanford University School of Medicine, Stanford, USA EW Petersdorf, Fred Hutchinson Cancer Center, Seattle, USA J Robinson, Anthony Nolan Research Institute, & University College London, London, UK J Trowsdale, Cambridge University, Cambridge, UK RE Bontrop, Biomedical Primate Research Centre, Rijswijk, The Netherlands K Osoegawa, Stanford Blood Center, Palo Alto, USA New sequences should be communicated to the WHO Nomenclature Committee for Factors of the HLA System via the sequence submission tool of the IPD-IMGT/HLA Database to receive official names, www.ebi.ac.uk/ipd/imgt/hla. The data that support the findings of this study are available from the corresponding author upon reasonable request.