HLA-DQ8

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.

DQ8 is commonly linked to autoimmune disease in the human population. DQ8 is the second most predominant isoform linked to coeliac disease and the DQ most linked to juvenile diabetes. DQ8 increases the risk for rheumatoid arthritis and is linked to the primary risk locus for RA, HLA-DR4. DR4 also plays an important role in juvenile diabetes. While the DQ8.1 haplotype is associated with disease, there is no known association with the DQB1*0305, DQ8.4 or DQ8.5 haplotypes (see infobox) with autoimmune disease; however, this may be the result of lack of study in populations that carry these and the very low frequency.

DQ8.1 also differs from other HLA in population frequencies. Typically for MHC Class II antigens in humans, haplotype frequencies do not exceed 40%. For example, in the US the highest haplotype frequency, the haplotype that encoded DQ6.2, is around 15%, this translates into phenotype frequencies of less than 30%. Atypically haplotype frequencies exceed 40%.

HLA-DQ4

HLA-DQ4 (DQ4) is a serotype subgroup within HLA-DQ(DQ) serotypes. The serotype is determined by the antibody recognition of β⁴ subset of DQ β-chains. The β-chain of DQ is encoded by HLA-DQB1 locus and DQ4 are encoded by the HLA-DQB1*04 allele group. This group currently contains 2 common alleles, DQB1*0401 and DQB1*0402. HLA-DQ4 and HLA-DQB1*04 are almost synonymous in meaning. DQ4 β-chains combine with α-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms. These isoforms, nicknamed DQ4.3 and DQ4.4, are also encoded by the DQA1*0303 and DQA1*0401 genes, respectively.

Serotype

Haplotypes

DQ4.3

DQA1*0303:DQB1*0401 is linked to DRB1*0405 and is common on the west Pacific rim, from Indonesia to Japan and inland areas of Eastern Asia. In Japan it confers susceptibility to juvenile diabetes likely via the DR4 gene.

DQA1*0303:DQB1*0402 is primarily found in Northeastern Asia and the west Pacific rim. It is similar to DQA1*0303:DQB1*0402.

DQ4.2

DQB1*0401:DQB1*0402 has a trimodal global distribution. The highest frequencies are found in the highland regions of the new world, peaking in NW Mexico and in the Andes. It is also found at high levels in Namibia and Botswana. Between these two population it is moderatedly high in the Ainu of northern Japan.

HLA-DQ6

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.

Serology

Alleles

DQB1*0601

DQB1*0601 is generally linked to DQA1*0103 as 6.1 haplotype. This haplotype is more common in Japan and other parts of East Asia.

DQB1*0602

DQB1*0602 is commonly linked to DQA1*0102 to form 6.2 haplotype. DQ6.2 and is common from Central Asia into Western Europe, *0602 is also linked to DQA1*0103 in parts of Asia.

DQB1*0603

DQB1*0603 is commonly linked to DQA1*0103 as 6.3 and is common from Central Asia into Western Europe, *0603 is also linked to DQA1*0102 in parts of Asia. In Europe it is most common in the Netherlands.