HLA-A1

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Further information: HLA serotypes explained
HLA-A1
(
heterodimer
SubunitsHLA-A*01--, β2-microglobulin
Older namesHL-A1
Subtypes
Subtype
allele
Available structures
A1 *01:01 1W72​
Rare alleles
Subtype
allele
Available structures
A1.2 *01:02
A1.3 *01:03
Alleles link-out to IMGT/HLA database at EBI

HLA-A1 (A1) is a human leukocyte antigen serotype within HLA-A "A" serotype group. The serotype is determined by the antibody recognition of α1 subset of HLA-A α-chains. For A1, the alpha "A" chain are encoded by the HLA-A*01 allele group and the β-chain are encoded by B2M locus.[1] This group currently is dominated by A*01:01. A1 and A*01 are almost synonymous in meaning. A1 is more common in Europe than elsewhere, it is part of a long haplotype that appears to have been frequent in the ancient peoples of Northwestern Europe. A1 is a frequent component of the AH8.1 haplotype. A1 serotype positivity is roughly linked to a large number of inflammatory diseases and conditions believed to have immune system involvement. Because of its linkage within the AH8.1 haplotype many studies showed association with A1 or A1,B8 only later to show the association drift toward the class II region gene alleles, DR3 and DQ2.5. While it is not clear what role A1 has in infectious disease, some linkage with infection rates in HIV remain associated within the A1 region of the haplotype.

Serotype

A1 recognition of some HLA A*01 gene products[2]
A*01 A1 Sample
allele % size (N)
*01:01 99 5612
*01:02 95  129
*01:03 78     9

In all instances so far, HLA-A1 has been found to be linked to disease by association, but there are few that define HLA-A1 has a predominant genetic risk relative to other gene-alleles in the vicinity of the A1 gene on the larger haplotype.

A1 and autoimmune diseases

A1 serotype was associated with a number of diseases as "HL-A"' antigens were first being described. The associations rapidly expanded to include 'HL-A8' HLA-B8, as the HLA A1 and B8 were found to be commonly linked. As DRw3 was characterized, autoimmune risk drifted toward the class II region.

Further information: Autoimmune disease in HLA A1-B8 haplotype

A1-B58 haplotype (A1-B17 where B58 is dominant) may remain associated with anti-neutrophil cytoplasmic antibody (ANCA)[3]

A1 in diabetes

With the exception of type 1 diabetes, most of the evidence for direct association of A1 with autoimmune diseases evaporated as DR3 and DQ2 genes were characterized. While type 1 diabetes shows an extended association on the HLA A1-B8-DR3-DQ2 haplotype, the association appears not to extend beyond the HLA-B locus.

type 1 diabetes but not Cw7-B8.[5]
The type 1 diabetes example shows the inherent difficulty in the use of linkage analysis alone to cipher risk.

A1 and allergic disease, sensitivities

Early in the study of HLA an association was found between HL A1,B8 in allergic disease, these are found to link to extended HLA A1-B8 region.

Further information: Allergies in HLA A1-B8 haplotype

Oddly, A1 was also found associated with

liver cirrhosis.[6] Whereas A1 was found negatively associated with other disease such as coal workers pneumoconiosis and leprosy.[7][8][9]

A1 and infectious disease

Within the early studies, A1 was found associate with or protected against some infectious diseases.[10][11][12] Some diseases found associated with A1 actually link to the extended A1-B8 haplotype, viral induced hepatitis and accelerated progression of HIV are examples.

Further information: Infectious disease and A1-B8 haplotype

A1 with B8 showed an increase risk of measles infection,[13] however, the significance was not consistent.[14] A more recent paper showed an association of A*01:01 with lower than average responses to measles vaccine.[15] With rubella, A1-B8 was more frequently found in people infected as a result of maternal transference.[16] A1 was also found to associate with circumoral

herpes simplex was also shown.[18]

A1 in Lymphoma

In Hodgkin's lymphoma HLA-A1,[19] but DR3 was not found higher.[20] The A1-B8-DR3-DQ2 haplotype has a known association with Enteropathy-associated T-cell lymphoma, approximately 70% of patients are homozygotes for DQ2 with at least one copy of DR3-DQ2.

Alleles

HLA A*01:01 frequencies
Study populationFreq.
 (in %)[21]
Ireland South25.0
England Lancaster21.5
Wales21.1
Ireland Northern20.2
England Sheffield19.7
England Liverpool19.4
England Newcastle19.3
Spain Basque Arratia Vall…19.2
England Leeds19.1
England Manchester18.9
Australia New South Wales18.7
Australia West18.5
Scotland Orkney17.0
South Africa Natal Tamil17.0
Belgium15.5
Italy North (1)15.4
Israeli Jews15.2
France South East15.0
German Essen14.4
Russia Arkhangelsk Pomors14.0
Nador Metalsa (Berber)13.7
Sweden Stockholm13.6
Spain Basque Gipuzkoa Pro…13.5
Burkina Faso Fulani13.3
Pakistan Sindhi13.3
Serbia13.2
Portugal Centre13.0
Sweden Uppsala County13.0
Czech Republic12.7
India Andhra Pradesh Goll…12.5
Israel Gaza Palestinians12.4
India Mumbai Marathas12.3
Tunisia12.3
Algeria112.3
Romanian12.2
Italy12.1
Russia Northwest11.9
Kenya Nandi11.8
Spain Eastern Andalusia11.4
Macedonia (4)11.3
Tunisia11.2
Turkey (I)10.9
Spain North Cantabrian10.8
Greece North10.0
Croatia9.7
Italy South Campania9.7
Greece (3)9.2
Brazil9.1
Finland8.9
Saudi Arabia8.7
Spain Catalonia Girona8.6
Pakistan Karachi Parsi8.3
Uganda Kampala8.3
Mongolia Khalkha8.0
Jordan Amman7.9
Spain North Cabuernigo7.6
Kenya Luo7.4
Bulgaria7.3
Russia Chuvash7.3
Oman7.2
Singapore Javanese Indone…7.0
Georgia Tbilisi Kurds6.7
France Corsica6.5
Georgia Tbilisi Georgian…5.7
Georgia Svaneti Svans5.6
China Qinghai Hui5.5
Australian Aborigine Cape…5.3
Sudanese5.0
Italy Sardinia(3)4.5
Russia Murmansk Saomi4.0
Spain Pas Valley3.8
Zambia Lusaka3.5
Burkina Faso Rimaibe3.2
Singapore Riau Malay3.2
Kenya3.1
Russia Nenets3.1
Cameroon Bakola Pygmy3.0
Thailand2.8
Australian Aborigine Groo…2.7
Senegal Niokholo Mandenka2.7
Cameroon Bamileke2.6
India Jalpaiguri Toto2.5
China Shanghai2.4
Thailand Northeast2.4
Allele frequencies presented, only
HLA A*01:02 frequencies
Study populationFreq.
 (in %)[21]
India North Delhi3.3
Kenya Nandi2.7
Cape Verde Southeastern I…1.6
Senegal Niokholo Mandenka1.6
Mali Bandiagara1.1
Tunisia1.0
Guinea Bissau0.8
Madeira0.8
USA African Americans (3)0.7
Argentina Toba Rosario0.6
USA Hispanic0.6
Kenya Luo0.4
Cameroon Beti0.3
Russia Tuva (2)0.3
Uganda Kampala0.3
Allele frequencies presented, only
HLA A*01:03 frequencies
Study populationFreq.
 (in %)[21]
Israel Ashkenazi and Non …2.1
Kenya Nandi1.7
Sudanese1.5
Kenya0.7
Saudi Arabia Guraiat and …0.7
Iran Baloch0.6
Ch. Guangdong Meizhou Han0.5
China Beijing Shijiazhuan…0.2
Allele frequencies presented, only

Most of the disease risk conferred by A*01:01 are represented by either A1 serotype risks, or A1-B8 serotype risk (In Europe A1-B8 is almost always composed of A*01:01 and B*08:01). The other alleles, A*01:02 and A*01:03, may confer specific risks. For example, A*01:02 was found linked to a type of stroke seen frequently in children with sickle cell anemia.[22]

There is a report that in the Somali communities within the US 2/3 of A1 bearers have the A*01:03 isoform.

A1-B haplotypes

  • A1-B8 Western Irish, N. Irish, Scottish, Wales, NW England, Scandinavia, Yugoslavia, Russia,....
  • A1-B7 Armenia, Austria, NW Europe (regional recombinant between A1-B8 and A2/A3-B7)
  • A1-B13 Uralic
  • A1-B35 (Albania, Belgium, Italy, Greece, France - Eastern Mediterranean in origin)
  • A1-B37 Yakuts, Tribal-India, Iyers-India, Mongolian, Indian, Orochon, Romanian, Yugoslavia, Korean, Albania, French, German, Manchu
  • A1-B51 Yugoslavia, Germany, Iberia, Italy
  • A1-B52 Bharghavas-India, Tribal-India, Italy, Iberia, France
  • A1-B57 (See tables on discussion page)
  • A1-B58 (See tables on discussion page)

References

  1. PMID 77067
    .
  2. ^ Allele Query Form IMGT/HLA - European Bioinformatics Institute
  3. PMID 15848045
    .
  4. PMID 18486765
    .
  5. PMID 12121673
    .
  6. S2CID 25032022
    .
  7. PMID 91226
    .
  8. PMID 453710
    .
  9. PMID 12975536
    .
  10. ^
    PMID 1198581
    .
  11. PMID 1236236
    .
  12. PMID 218441
    .
  13. PMID 1138435
    .
  14. PMID 512353
    .
  15. S2CID 25508939
    .
  16. S2CID 36212779
    .
  17. PMID 596908
    .
  18. PMID 1797451
    .
  19. S2CID 5400650
    .
  20. PMID 143667
    .
  21. ^
    PMID 12753660
    .
  22. PMID 12517810
    .
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