# HLA-B51

HLA-B51 (B51) is an HLA-B serotype. The serotype identifies the more common HLA-B*51 gene products.
B51 is a split antigen of the broad antigen B5, and is a sister serotype of B52. There are many alleles within the B*51 allele group. B51 is associated with several diseases, including Behçet's disease.

## Serotype

Serotypes B51, B5, B52, and B53 recognition of some HLA B*51 allele-group gene products :
| B*51 | B51 | B5 | B52 | B53 | Sample |
| allele | % | % | % | % | size (N) |
| *5101 | 96 | 2 | 1 | | 1899 |
| *5102 | 73 | 3 | 6 | 11 | 218 |
| *5104 | 83 | 17 | | | 6 |
| *5105 | 48 | | 16 | 24 | 25 |
| *5106 | 64 | | 7 | 12 | 42 |
| *5107 | 78 | | 9 | | 68 |
| *5108 | 77 | | | 3 | 154 |
| *5109 | 86 | | | | 43 |
| B**5102 also reacts to B5102 - 3%, **5103 with B5103 ||||||
| Alleles link-out to IMGT/HLA Databease at EBI ||||||

## Alleles

There are 71 alleles, 57 amino acid sequence variants in B51 of which 4 are nulls. Of these only 9 are frequent enough to have been reliably serotyped. B*5101 is the most common, but others have a large regional abundance.
HLA B*5101 frequencies :
| | | freq |
| ref. | Population | (%) |
| | Bulgaria | 20.9 |
| | Georgia Tbilisi Georgians | 15.7 |
| | India Tamil Nadu Nadar | 15.6 |
| | China North Han | 14.8 |
| | Georgia Tbilisi Kurds | 12.1 |
| | India Andhra Pradesh Golla | 12.0 |
| | China Qinghai Hui | 11.4 |
| | India New Delhi | 9.8 |
| | Madeira | 9.7 |
| | South Africa Natal Tamil | 9.2 |
| | USA Hawaii Okinawa | 8.7 |
| | Cape Verde Northwestern Islands | 8.1 |
| | Cape Verde Southeastern Islands | 7.3 |
| | India Mumbai Marathas | 6.8 |
| | Russia Tuva pop 2 | 6.1 |
| | Israel Arab Druse | 6.0 |
| | China Inner Mongolia | 5.9 |
| | Czech Republic | 5.7 |
| | Finland | 5.6 |
| | Iran Baloch | 8.1 |
| | Brazil | 5.1 |
| | Mexico Guadalajara Mestizos | 4.9 |
| | New Mexico Canoncito Navajo | 4.9 |
| | China South Han | 4.6 |
| | India North Hindus | 3.8 |
| | Thailand | 3.1 |
| | Ivory Coast Akan Adiopodoume | 2.3 |
| | Singapore Chinese Han | 2.3 |
| | Singapore Javanese Indonesians | 2.0 |
| | Taiwan Saisiat | 2.0 |
| | Kenya | 1.7 |
| | Cameroon Yaounde | 1.6 |
| | Senegal Niokholo Mandenka | 1.6 |
| | Guinea Bissau | 1.5 |
| | USA Arizona Pima | 1.1 |
| | Venezuela Perja Mountain Bari | 1.1 |
| | Taiwan Pazeh | 0.9 |
| | China Guangdong Meizhou Han | 0.5 |
| | Israel Ashk. & Non Ashk. Jews | 0.5 |
| | Singapore Thai | 3.0 |
| | Iran Baloch | 1.0 |
| | USA Asian | 1.0 |

## Disease associations
### By serotype

Bw51 was associated with Behçet's disease, in endemic (versus epidemic) mucocutaneous lymph node syndrome, susceptibility to the virus that causes German measles infection.
HLA B*5102 frequencies :
| | | freq |
| ref. | Population | (%) |
| | Mexico Sonora Seri | 1.5 |
| | Thailand | 1.4 |
| | Singapore Chinese | 1.3 |
| | Hong Kong Chinese | 1.0 |
| | USA Natives | 0.8 |
| | Mexico Zaptotec Oaxaca | 0.7 |
| | South Korea pop 3 | 0.6 |
| | Shijiazhuang Tianjian Han | 0.5 |
| | China Guangxi Maonan | 0.5 |
| | Japan (5) | 0.4 |
| | USA Asian | 0.4 |
| | USA Hispanic | 0.4 |
| | USA African America | 0.2 |

## In Behçet's disease

Behçet's disease is an inflammation of the wall of blood vessels that can involve the eyes, skin, and the rest of the body. Several alleles of B51 (B*5101, B*5108, B*5105, and B*5104) are found in disease, and linkage to markers, D6S285, in the HLA locus was strong (P<0.005). Homozygotes of B51 showed considerably high risk for disease indicating a possible gene-dose effect. B51 is capable of distinguishing several varieties of disease. HLA-B51 is found more frequently in disease that has an eye involvement. However it is less common in some regions when there is increased neurological involvement. The MICA*009 allele has been found to also associated with ABD when B51 is also present, IL-8 and other cytokines may also be involved. Sister chromatid exchange has also been observed more frequently in B51(+) ABD.
However, B51 tends not to be found in ABD when a certain SUMO4 gene variant is involved, and symptoms appear to be milder when HLA-B27 is present.