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Further information: HLA serotypes explained
(MHC Class I, A cell surface antigen)
Illustration HLA-A.png
Protein transmembrane receptor/ligand
Structure αβ heterodimer
Subunits HLA-A*2301, β2-microglobulin
Older names HL-A9
Available structures
A23 *2301
Alleles link-out to IMGT/HLA database at EBI

HLA-A23 (A23) is a human leukocyte antigen serotype within HLA-A serotype group. The serotype is determined by the antibody recognition of α23 subset of HLA-A α-chains. For A23, the alpha, "A", chain are encoded by the HLA-A*23 allele group and the β-chain are encoded by B2M locus.[1] This group currently is dominated by A*2301. A23 and A*23 are almost synonymous in meaning. A23 is a split antigen of the broad antigen HLA-A9 and it is a sister serotype of HLA-A24.

A23 is common in Africa and regions of the Middle East, Mediterranean, and India than Europe, East Asia or the Americas.


A23 recognition of some HLA A*23 gene products[2]
A*23 A23 A24 Sample
allele  %  % size (N)
*2301 95 1 5119


HLA A*2301 frequencies
Study population Freq.
 (in %)[3]
Mali Bandiagara 22.8
Cameroon Yaounde 18.7
Senegal Niokholo Mandenka 17.7
Guinea Bissau 15.6
Cameroon Bamileke 14.9
Cape Verde Southeastern I… 14.8
Cameroon Beti 13.5
Zimbabwe Harare Shona 12.7
USA African America 11.1
Portugal North 10.9
South African Natal Zulu 10.0
Cuban Mulatto 9.5
Tunisia 9.4
Kenya Luo 8.9
Morocco Berber Nador Meta… 8.2
Zambia Lusaka 8.1
China Beijing 7.5
Kenya Nandi 7.1
Uganda Kampala 6.8
Georgia Tibilisi Kurds 6.7
Portugal South 6.1
Sudanese 5.8
Bulgaria 5.5
Israel Arab Druse 5.5
Saudi Arabia Guraiat and … 5.4
Spain Catalonia Girona 4.6
Kenya 4.5
Venezuela Caracus 4.0
USA South Texas Hispanics 3.9
Mexico Mestizos 3.7
Russia Tuva pop 2 2.9
Romanian 2.5
Croatia 2.3
Brazil 2.0
Spain Basque Gipuzkoa Pro… 2.0
Australia New South Wales 1.9
Czech Republic 1.9
Georgia Tibilisi Georgian… 1.9
Oman 1.7
Belgium 1.6
USA North American Native… 1.6
China Inner Mongolia 1.5
India New Delhi 1.5
Pakistan Pathan 1.5
Ireland Northern 1.4
Jordan Amman 1.4
Mongolia Buriat 1.4
Pakistan Sindhi 1.3
USA Caucasian (2) 1.3
France South East 1.2
Italy North Pavia 1.2
Iran Baloch 1.1
Italy Bergamo 1.1
France Corsica 1.0
India North Hindus 1.0
Portugal Centre 1.0
Allele frequencies presented, only


A23-B7 is found in N.Afr. and S.Afr non-caucasians.
A23-B44 is found in Albania, Zimbabwe, Morocco, Spain and Danes.
A23-B58 is found in the !kung and Zaire.

Associated diseases[edit]

A*23:Cw*07 is associated with higher viral load in HIV[4]


  1. ^ Arce-Gomez B, Jones EA, Barnstable CJ, Solomon E, Bodmer WF (February 1978). "The genetic control of HLA-A and B antigens in somatic cell hybrids: requirement for beta2 microglobulin". Tissue Antigens. 11 (2): 96–112. doi:10.1111/j.1399-0039.1978.tb01233.x. PMID 77067. 
  2. ^ Allele Query Form IMGT/HLA - European Bioinformatics Institute
  3. ^ Middleton D, Menchaca L, Rood H, Komerofsky R (2003). "New allele frequency database: http://www.allelefrequencies.net". Tissue Antigens. 61 (5): 403–7. doi:10.1034/j.1399-0039.2003.00062.x. PMID 12753660. 
  4. ^ Tang J, Tang S, Lobashevsky E, Myracle A, Fideli U, Aldrovandi G, Allen S, Musonda R, Kaslow R (2002). "Favorable and unfavorable HLA class I alleles and haplotypes in Zambians predominantly infected with clade C human immunodeficiency virus type 1.". J Virol. 76 (16): 8276–84. doi:10.1128/JVI.76.16.8276-8284.2002. PMC 155130Freely accessible. PMID 12134033.