HLA-B7

major histocompatibility complex (human), class I, B7
Alleles	B*0702, *0703, *0704, *0705
Structure (See HLA-B)
Alleles (See Serotyping)
Locus	chr.6 6p21.31

HLA-B7 (B7) is an HLA-B serotype. The serotype identifies the more common HLA-B*07 gene products.^[1] (For terminology help see: HLA-serotype tutorial) B7, previously HL-A7, was one of the first 'HL-A' antigens recognized, largely because of the frequency of B*0702 in Northern and Western Europe and the United States. B7 is found in two major haplotypes in Europe, where it reaches peak frequency in Ireland. One haplotype A3-B7-DR15-DQ1 can be found over a vast region and is in apparent selective disequilibrium. B7 is a risk factor for cervical cancer, sarcoidosis, and early-onset spondylarthropathies.

Serology

B7 serotype recognition of Some HLA B*07 allele-group gene products^[2]

B*07	B7	Sample
allele	%	size (N)
*0702	98	10841
*0703	93	15
*0704	89	44
*0705	95	42
*0706	96	23
*0707	92	13
*0709	78	9
Alleles link-out to IMGT/HLA Databease at EBI

Alleles

HLA B*0702 frequencies

		freq
ref.	Population	(%)
[3]	Ireland South	17.6
[3]	Ireland Northern	17.3
[3]	Australia New South Wales	12.0
[3]	Croatia	9.7
[3]	Azores S. Maria & Miguel	9.0
[3]	Cameroon Beti	8.6
[3]	Saudi Arabia Guraiat and Hail	8.3
[3]	Azores Central Islands	8.0
[3]	France South East	7.2
[3]	Cameroon Bamileke	7.1
[3]	Portugal Centre	7.0
[3]	Italy North pop 1	6.7
[3]	Japan Central	6.5
[3]	Czech Republic	6.1
[3]	Uganda Kampala	5.9
[3]	Mali Bandiagara	5.8
[3]	Senegal Niokholo Mandenka	5.8
[3]	India Mumbai Marathas	4.9
[3]	Zambia Lusaka	4.6
[3]	Zimbabwe Harare Shona	4.6
[3]	South Africian Natal Zulu	4.5
[3]	Romanian	3.7
[3]	South Korea (3)	3.5
[3]	Shijiazhuang Tianjian Han, China	3.4
[3]	India North Delhi	3.3
[3]	Kenya Luo	2.5
[3]	China Guangzhou Han	2.4
[3]	Mexico Chihuahua Tarahumara	2.3
[3]	Sudanese	2.3
[3]	Singapore Javanese Indonesians	2.0
[3]	Spain Eastern Andalusia Gipsy	2.0
[3]	New Caledonia	1.9
[3]	Oman	1.7
[3]	USA Alaska Yupik Natives	1.6
[3]	China Beijing	1.5
[3]	Tunisia	1.5
[3]	Argentina Toba Rosario	1.2
[3]	Singapore Chinese Han	1.2
[3]	USA Arizona Pima	1.1
[3]	American Samoa	1.0
[3]	Japan Ainu Hokkaido	1.0
[3]	Kenya Nandi	1.0
[3]	Portugal South	1.0
[3]	Singapore Riau Malay	1.0
[3]	Singapore Thai	1.0

In disease

Cervical cancer

HLA-B7 along with HLA-DQ8 increased risk for cervical cancer in at risk Costa Rican women^[4] and Asian Indians^[5]

Sarcoidosis

A relationship between HLA-B7 and sarcoidosis has been known for 30+ years.^[6] However the association is weak and has not been reproducible in all studies. A common serologically defined haplotype in Europeans is HLA A3-Cw7-B7-DR15-DQ6.2 which is composed of alleles A*0301:Cw*0701:B*0702:DRB1*1501:DQA1*0102:DQB1*0602. In persistent sarcoidosis this haplotype was found to be increased in sarcoidosis, and further study eliminated risk contributed by A3-Cw7 and DQ6.2 indicating B7-DR15 haplotype contains risk of disease (OR = 2.5). The region of chromosome 6 contains nearly on million nucleotides so that these genes, or a closely linked gene could be involved in disease.^[7]

Juvenile Spondylarthropathies

In Croatian children, two HLA-B27 alleles were found associated with disease, B*2702, B*2705.^[8] The study showed also B*0702 in cooperation with B*27, the HLA-B*07/B*27 combination with D6S273-134 genomic marker allele and was found not to be the result of linkage disequilibrium. B*2705 was found to be dominant allele associated.

Haemochromatosis

The HFE gene responsible for haemochromatosis is distal on chromosome 6 from HLA-A and more so from HLA-B, the distance suffices (3 million nucleotides) to allow equilibration of the loci. Nonetheless, a linkage has been found between A3-B7 haplotype and haemochromatosis. The region is almost 1.4 million nucleotides in length and contains many other genes that could be involved. A more recent study looked at a number of linked gene-alleles and found I82-2:D6S265-1:HLA-A3:D6S128-2:HLA-F1:D6S105-8 was constantly associated while B7 appeared beyond the haplotype linked to disease.^[9]

References

1. Marsh SG, Albert ED, Bodmer WF, et al. (2005). "Nomenclature for factors of the HLA system, 2004". Tissue Antigens 65 (4): 301–69. doi:10.1111/j.1399-0039.2005.00379.x. PMID 15787720.
2. derived from IMGT/HLA
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. External link in |title= (help)
4. Wang SS, Wheeler CM, Hildesheim A, et al. (November 2001). "Human leukocyte antigen class I and II alleles and risk of cervical neoplasia: results from a population-based study in Costa Rica". J. Infect. Dis. 184 (10): 1310–4. doi:10.1086/324209. PMID 11679920.
5. Bhattacharya P, Sengupta S (October 2007). "Predisposition to HPV16/18-related cervical cancer because of proline homozygosity at codon 72 of p53 among Indian women is influenced by HLA-B*07 and homozygosity of HLA-DQB1*03". Tissue Antigens 70 (4): 283–93. doi:10.1111/j.1399-0039.2007.00894.x. PMID 17767549.
6. Rybicki BA, Iannuzzi MC (March 2004). "Sarcoidosis and human leukocyte antigen class I and II genes: it takes two to tango?". Am. J. Respir. Crit. Care Med. 169 (6): 665–6. doi:10.1164/rccm.2401005. PMID 15003948.
7. Grunewald J, Eklund A, Olerup O (March 2004). "Human leukocyte antigen class I alleles and the disease course in sarcoidosis patients". Am. J. Respir. Crit. Care Med. 169 (6): 696–702. doi:10.1164/rccm.200303-459OC. PMID 14656748.
8. Harjacek M, Margetić T, Kerhin-Brkljacić V, Martinez N, Grubić Z (2008). "HLA-B*27/HLA-B*07 in combination with D6S273-134 allele is associated with increased susceptibility to juvenile spondyloarthropathies". Clin. Exp. Rheumatol. 26 (3): 498–504. PMID 18578977.
9. Raha-Chowdhury R, Bowen DJ, Burnett AK, Worwood M (June 1995). "Allelic associations and homozygosity at loci from HLA-B to D6S299 in genetic haemochromatosis". J. Med. Genet. 32 (6): 446–52. doi:10.1136/jmg.32.6.446. PMC 1050484. PMID 7666396.