HLA-DQ7

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Illustration of HLA-DQ with peptide in the binding pocket
major histocompatibility complex, class II, DQ7
Haplotypes DQA1*03:02:DQB1*03:01 DQA1*03:03:DQB1*03:01 DQA1*04:01:DQB1*03:01 DQA1*05:05:DQB1*03:01 DQA1*06:01:DQB1*03:01
Structure (See HLA-DQ)
Identifiers
alpha 1 *0302 *0303 *0401 *0505 *0601
Symbol(s) HLA-DQA1[permanent dead link]
EBI-HLA DQA1*0302
EBI-HLA DQA1*0303
EBI-HLA DQA1*0401
EBI-HLA DQA1*0505
EBI-HLA DQA1*0601
Identifiers
beta 1 *0301 *0304
Symbol(s) HLA-DQB1
EBI-HLA DQB1*0301
EBI-HLA DQB1*0304
Shared data
Locus
chr.6 6p21.31

HLA-DQ7 (DQ7) is an HLA-DQ serotype that recognizes the common HLA DQB1*0301[1] and the less common HLA DQB1*0304 gene products. DQ7 is a form of 'split antigen' of the broad antigen group DQ3 which also contains DQ8 and DQ9.

DQ7 is linked by haplotype to a number of DQA1 (DQ alpha chain) genes, producing in cis-haplotype form, a large number of DQ αβ isoforms. These DQ alpha chains are also known to form transhaplotype isomers with other HLA-DQ.

DQ7 is linked to the following alpha chains genes (DQA1*)

  • 03 – *0301, *0302, *0303
  • 0401
  • 0505
  • 0601

Serology

DQ3, DQ7, DQ8, and DQ9 recognition of Some DRB1*and [2]
DQB1* DQ7 DQ3 DQ8 Sample
allele % % % size (N)
0301 85 40 1 12220
0304 40 35 8 111

Serotyping efficiency. The serotyping efficiency of DQ7 toward DQB1*0301 is reasonably good, but still results in some false negatives, for *0304 the typing efficiency is poor and cross-reaction with DQ8 is relatively high.

Alleles

DQB1*0301

DQB1*0301 is the major DQ7 allele DQB1*0301 appears to be associated with lupus anticoagulant.[3]

DQB1*0304

DQB1*0304 is the minor DQ7 allele

Haplotypes

HLA DQA1*03:DQB1*0301 frequencies
freq
ref. Population (%)
[4] Chukotka Chukchi (Siberia) 26.7
[4] Chukotka Eskimos (Siberia) 25.0
[4] Koryaks (NE Kamchatka, Siberia) 19.1
[4] Polygus Evenks (Siberia) 11.4
[4] Khalkh (Ulaanbaatar, Mongolia) 11.0
[4] Negidal (Siberia) 9.6
[4] Kushun Buryat (Siberia) 8.0
[4] Tarialan Khoton (Mongolia) 7.8
[4] France Ceph 6.0
[4] Russia Tuva (2) 6.0
[4] Udegeys Gvaysugi (Siberia) 4.8
[4] Irkutsk Tofalar (Siberia ) 4.7
[4] Ulchi (Siberia) 4.1
[4] Belgian pop2 4.1
[4] England Caucasoid 4.0
[4] Italy pop 2 2.8
[4] Russia Tuva Todja 2.3
[4] China Ürümqi Kazak 2.4
[4] Sulamai Kets (Siberia) 2.3
[4] Russia Siberia Nganasan Dudinka 2.1
[4] NW Slavic Russia 2.0
[4] Japan Fukuoka 1.2
[4] Japan (2) 1.1

DQ haplotypes of this serotype are formed between the cis-chromosomal genes of the DQA1 locus. This includes DQA1*0301, *0302, *0303, *0401, *0505, *0601.

There is a rather large degree of disequilibration about DQA1*0301 suggesting that this is one of the older and more established HLA DQB1* alleles in Eurasia. The intron structure of DQB1 suggest that DQB1*0301 DQB1*0302/*0303 split occurred before DQB1*0302/*0303, the distribution of *03 in Africa suggest that recombination DQA1*03:DQB1*0301 are primarily the result of recombination events that have occurred in Africa. A recent study of myasthenia gravis in Houston confirms the presence of A*0505:B*0301 in Nigeria. B1*0301 and A1*03 haplotypes are found at relatively high frequencies in SE Asia and Austronesia, also indicating that it is well established in the exo-African population.

DQ7.3

The DQ7.3 haplotype can be formed by DQA1*0301:DQB1*0301, DQA1*0302:DQB1*0301, DQA1*0303:DQB1*0301. In the west, the DQA1*0303:DQB1*0301 haplotype appears to be more common. The gene products of all 3 function similarly and subunits are interchangeable. In the literature, older DNA tests recognize DQA1*0303 as DQA1*0302, and still oldest DNA tests recognize all three as DQA1*03 or DQA1*0301.

DQA1*0303:DQB1*0301 may be involved in narcolepsy.[5] DQ7.3 appears to be associated with oral ulcerations and gingival disease [6]

DQ7.4

HLA DQA1*0401:DQB1*0301
freq
ref. Population (%)
[4] Chukotka Chukchi (Siberia) 9.5
[4] Gvaysugi Udegeys (Siberia) 9.5
[4] Chukotka Eskimos (Siberia) 8.7
[4] Polygus Evenks (Siberia) 7.2
[4] NE Koryaks (Kamchatka) 6.5
[4] Cameroon Saa 4.4
[4] Sulamai Kets (Siberia) 2.3
[4] Gambia 1.4
[4] Fukuoka Japan 1.2
[7] Caucasian Americans 0.3

DQA1*0401:DQB1*0301 (DQ7.4) This haplotype is found in Siberia, Africa but also at low levels in Western Europe.

DQ7.5

HLA DQA1*0505 frequencies
freq
ref. Population (%)
[4] Lebanon (estimated) 40.0
[4] Italy Rome 29.6
[4] Netherlands (2) 15.5
[4] Tunisia 14.6
[4] England (2) 10.1
[4] South Korea 6.8
[4] Congo Kinshasa Bantu 4.4

DQA1*0505:DQB1*0301 (DQ7.5) was gene-typed as DQA1*0501:DQB1*0301 until it was recognized that there was amino acid sequence variant in the preprocessed DQA1* gene product (proto-α-chain

juvenile diabetes, which appears to be more common among cereal eating peoples.[9] Cereals were first domesticated in the Near and Middle East more than 10,000 years ago and selection may explain DQ7.5's higher frequencies. (See: Triticeae
)

The processed alpha subunit of DQA1*0505 is identical to that of DQA1*0501, but some slight differences in the association with autoimmune disease are observed, possibly as a result of linked DR and DQB1 genes. DQA1*0505 can play into celiac disease under two circumstances. First it can increase risk when DQ2.5 is present, although current studies indicate that it marginally increases risk relative to DQB1*0202 in DQ2.5 cis haplotype. DQA1*0505, without DQ2, is found in a small percentage of coeliac disease (without DQ2 or DQ8).[10]

DQ7.5 is found also high in frequency in the new world, but with

warts, limited cutaneous systemic sclerosis in Africans, and primary sclerosing cholangitis in Southern Europeans. DQB1*0301 is also predisposing in narcolepsy.[5] DQB1*0301 does not to play a role in any frequently occurring autoimmune disease and its presence in the near east and suppressed frequencies of coeliac disease and Type 1 diabetes in these regions is suggestive that it has a positive selection in Post-Mesolithic
cereal based societies in the Western Eurasia.

DQB1*0301 appears to be more associated with early onset myasthenia gravis in Japanese than DQ8, and was also found along with DQB1*0304 to be associated with Chinese MG. DQ7 or associated DR types may play a role in rheumatoid arthritis. In celiac disease the DQ7 (A*0505/1) can mediate celiac disease when HLA DQ2.2 is also present. HLA DQB1*0301 in Turks is associated with Thymoma but the risk may be associated with HLA class I loci.

DQ7.6

HLA DQA1*0601 frequencies
freq
ref. Population (%)
[4] Java Yogyakarta 48.1
[4] Kiribati 37.9
[4] Nauru 28.4
[4] Harbin City (Manchuria, China) 12.8
[4] Thailand 12.7
[4] South Korean (5) 4.4
[4] China Beijing and Xian 3.5
[4] Japan 3.0
[4] India Bombay 1.7
[4] England Caucasoid 0.6
[4] Italy Central 0.6
[4] Algeria1 0.5
[4] Cameroon 0.4

DQA1*0601:DQB1*0301 (DQ7.6) is a globally rare haplotype, however it is found at high frequencies in the South Pacific and along the West Pacific rim. DQB1*0301 appears to be uniquely linked to DQA1*0601. DQ7.6 is positively associated with

pulmonary tuberculosis.[16]

References

  1. PMID 7905469
    .
  2. ^ derived from IMGT/HLA
  3. PMID 1673688
    .
  4. ^
    PMID 12753660
    .
  5. ^
    PMID 17207713
    .
  6. PMID 8052655
    .
  7. PMID 12974796
    .
  8. PMID 10777105
    .
  9. PMID 16988007
    .
  10. PMID 12651074
    .
  11. PMID 17465466
    .
  12. PMID 11802952
    .
  13. PMID 7788177
    .
  14. PMID 7624445
    .
  15. PMID 9602373
    .
  16. PMID 12358854
    .

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