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. [5] 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.
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). [5]
The beta chain is approximately 26-28 kDa and it contains 6 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. [5] [6]
A four-loci genotype study showed that A*01-B*07-DRB1*0701- DQB1*0602 (P = 0.001, OR 41.9) and the A*31-B*51-DRB1*0103- DQB1*0302 (P = 0.012, OR 4.8) are positively associated with autism among Saudi patients.
Several alleles of HLA-DQB1 are associated with an increased risk of developing type 1 diabetes. [7] [8] [9] 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).
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. [10]
Certain HLA-DQB1 alleles are also linked to a modest increased risk of multiple sclerosis. [11] [12]
Other HLA-DQB1 alleles are associated with a predisposition to narcolepsy, [13] specifically HLA-DQB1*0602, which is carried by over 90% of patients with narcolepsy-cataplexy. [14]
| 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 |
The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules.
The human leukocyte antigen (HLA) system or complex is a complex of genes on chromosome 6 in humans which encode cell-surface proteins responsible for regulation of the immune system. The HLA system is also known as the human version of the major histocompatibility complex (MHC) found in many animals.
HLA-DR is an MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31. The complex of HLA-DR and peptide, generally between 9 and 30 amino acids in length, constitutes a ligand for the T-cell receptor (TCR). HLA were originally defined as cell surface antigens that mediate graft-versus-host disease. Identification of these antigens has led to greater success and longevity in organ transplant.
HLA class II histocompatibility antigen, DRB1 beta chain is a protein that in humans is encoded by the HLA-DRB1 gene. DRB1 encodes the most prevalent beta subunit of HLA-DR. DRB1 alleles, especially those encoding amino acid sequence changes at positions 11 and 13, are associated risk of rheumatoid arthritis.
MHC Class II molecules are a class of major histocompatibility complex (MHC) molecules normally found only on professional antigen-presenting cells such as dendritic cells, mononuclear phagocytes, some endothelial cells, thymic epithelial cells, and B cells. These cells are important in initiating immune responses.
HLA-DQ (DQ) is a cell surface receptor protein found on antigen-presenting cells. It is an αβ heterodimer of type MHC class II. The α and β chains are encoded by two loci, HLA-DQA1 and HLA-DQB1, that are adjacent to each other on chromosome band 6p21.3. Both α-chain and β-chain vary greatly. A person often produces two α-chain and two β-chain variants and thus 4 isoforms of DQ. The DQ loci are in close genetic linkage to HLA-DR, and less closely linked to HLA-DP, HLA-A, HLA-B and HLA-C.
HLA DR3-DQ2 is double serotype that specifically recognizes cells from individuals who carry a multigene HLA DR, DQ haplotype. Certain HLA DR and DQ genes have known involvement in autoimmune diseases. DR3-DQ2, a multigene haplotype, stands out in prominence because it is a factor in several prominent diseases, namely coeliac disease and juvenile diabetes. In coeliac disease, the DR3-DQ2 haplotype is associated with highest risk for disease in first degree relatives, highest risk is conferred by DQA1*0501:DQB1*0201 homozygotes and semihomozygotes of DQ2, and represents the overwhelming majority of risk. HLA DR3-DQ2 encodes DQ2.5cis isoform of HLA-DQ, this isoform is described frequently as 'the DQ2 isoform', but in actuality there are two major DQ2 isoform. The DQ2.5 isoform, however, is many times more frequently associated with autoimmune disease, and as a result to contribution of DQ2.2 is often ignored.
HLA-DQ8 (DQ8) is a human leukocyte antigen serotype within the HLA-DQ (DQ) serotype group. DQ8 is a split antigen of the DQ3 broad antigen. DQ8 is determined by the antibody recognition of β8 and this generally detects the gene product of DQB1*0302.
HLA-DQ2 (DQ2) is a serotype group within HLA-DQ (DQ) serotyping system. The serotype is determined by the antibody recognition of β2 subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ2 are encoded by the HLA-DQB1*02 allele group. This group currently contains two common alleles, DQB1*0201 and DQB1*0202. HLA-DQ2 and HLA-DQB1*02 are almost synonymous in meaning. DQ2 β-chains combine with α-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, nicknamed DQ2.2 and DQ2.5, are also encoded by the DQA1*0201 and DQA1*0501 genes, respectively.
HLA-DQ5 (DQ5) is a human leukocyte antigen serotype subgroup within HLA-DQ(DQ) serotypes. The serotype is determined by the antibody recognition of β5.x subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ5 are encoded by the HLA-DQB1*05 allele group. This group currently contains 4 common alleles, DQB1*0501, *0502, *0503, and *0504. HLA-DQ5 and HLA-DQB1*05 are almost synonymous in meaning. DQ5 β-chains combine with α-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, are all HLA-DQ1 encoded by the DQA1*01 allele group.
HLA-DQ6 (DQ6) is a human leukocyte antigen serotype within HLA-DQ (DQ) serotype group. The serotype is determined by the antibody recognition of β6 subset of DQ β-chains. The β-chain of DQ isoforms are encoded by HLA-DQB1 locus and DQ6 are encoded by the HLA-DQB1*06 allele group. This group currently contains many common alleles, DQB1*0602 is the most common. HLA-DQ6 and DQB1*06 are almost synonymous in meaning. DQ6 β-chains combine with α-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. For DQ6, however, cis-isoform pairing only occurs with DQ1 α-chains. There are many haplotypes of DQ6.
HLA-DQ9 (DQ9) is a human leukocyte antigen serotype within the HLA-DQ (DQ) serotype group. DQ9 is a split antigen of the DQ3 broad antigen. DQ9 is determined by the antibody recognition of β9 and this generally detects the gene product of DQB1*0303.
HLA-DQ7 (DQ7) is an HLA-DQ serotype that recognizes the common HLA DQB1*0301 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.
Major histocompatibility complex, class II, DR beta 4, also known as HLA-DRB4, is a human gene.
HLA class II histocompatibility antigen, DRB5 beta chain is a protein that in humans is encoded by the HLA-DRB5 gene.
HLA-DR4 (DR4) is an HLA-DR serotype that recognizes the DRB1*04 gene products. The DR4 serogroup is large and has a number of moderate frequency alleles spread over large regions of the world.
Major histocompatibility complex, class II, DQ alpha 1, also known as HLA-DQA1, is a human gene present on short arm of chromosome 6 (6p21.3) and also denotes the genetic locus which contains this gene. 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.
HLA class II histocompatibility antigen, DP(W2) beta chain is a protein that in humans is encoded by the HLA-DPB1 gene.
Major histocompatibility complex, class II, DQ beta 3, also known as HLA-DQB3, is a human gene and also denotes the genetic locus which contains this gene. While the overall sequence of the protein encoded by this gene is similar to other HLA class II beta chains, the translated protein is lacking several domains and therefore it is not clear that this gene encodes a functional protein.
HLA B7-DR15-DQ6 is a multigene haplotype that covers a majority of the human major histocompatibility complex on chromosome 6. A multigene haplotype is set of inherited alleles covering several genes, or gene-alleles, common multigene haplotypes are generally the result of descent by common ancestry. Chromosomal recombination fragments multigene haplotypes as the distance to that ancestor increases in number of generations.
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