HLA-DQB1
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Major histocompatibility complex, class II, DQ beta 1, also known as HLA-DQB1, is a human gene and also denotes the genetic locus that contains this gene.[1] The protein encoded by this gene is one of two proteins that are required to form the DQ heterodimer, a cell surface receptor essential to the function of the immune system.
Contents
Function
HLA-DQB1 belongs to the HLA class II beta chain paralogues. This class II molecule is a heterodimer consisting of an alpha (DQA) and a beta chain (DQB), both anchored in the membrane. It plays a central role in the immune system by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen-presenting cells (APC: B lymphocytes, dendritic cells, macrophages).[1]
Gene structure and polymorphisms
The beta chain is approximately 26-28 kDa and it contains 5 exons. Exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular protein domains, exon 4 encodes the transmembrane domain, and exon 5 encodes the cytoplasmic tail. Within the DQ molecule, both the alpha chain and the beta chain contain the polymorphisms specifying the peptide binding specificities, resulting in up to 4 different molecules. Typing for these polymorphisms is routinely done for bone marrow transplantation.[1][2]
Disease association
Diabetes
Several alleles of HLA-DQB1 are associated with an increased risk of developing type 1 diabetes.[3][4][5] The locus also has the genetic name IDDM1 as it is the highest genetic risk for type 1 diabetes. Again the DQB1*0201 and DQB1*0302 alleles, particularly the phenotype DQB1*0201/*0302 has a high risk of late onset type 1 diabetes. The risk is partially shared with the HLA-DR locus (DR3 and DR4 serotypes).
Celiac disease
Celiac1 is a genetic name for DQB1, the HLA DQB1*0201, *0202, and *0302 encode genes that mediate the autoimmune coeliac disease. Homozygotes of DQB1*0201 have a higher risk of developing the celiac disease, relative to any other genetic locus.[6]
Multiple sclerosis
Certain HLA-DQB1 alleles are also linked to a modest increased risk of multiple sclerosis.[7][8]
Narcolepsy
Other HLA-DQB1 alleles are associated with a predisposition to narcolepsy,[9] specifically HLA-DQB1*0602, which is carried by over 90% of patients with narcolepsy-cataplexy.[10]
Alleles
| Serotype | DQB1 allele |
|---|---|
| DQ2 | *0201 |
| *0202 | |
| *0203 | |
| DQ4 | *0401 |
| *0402 | |
| DQ5 | *0501 |
| *0502 | |
| *0503 | |
| *0504 | |
| DQ6 | *0601 |
| *0602 | |
| *0603 | |
| *0604 | |
| *0605 | |
| *0609 | |
| DQ7 | *0301 |
| *0304 | |
| DQ8 | *0302 |
| *0305 | |
| DQ9 | *0303 |
See also
References
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