HLA-A2

HLA-A2 (A2) is a human leukocyte antigen serotype within HLA-A "A" serotype group. The serotype is determined by the antibody recognition of α2 subset of HLA-A α-chains. For A2, the alpha "A" chain are encoded by the HLA-A*02 allele group and the β-chain are encoded by B2M locus. A2 and A*02 are almost synonymous in meaning. A2 is more common in Northern Asia and North America than elsewhere, and it is part of a several long haplotypes.

The serotype identifies the gene products of many HLA-A*02 alleles, including HLA-A*0201, *0202, *0203, *0206, and *0207 gene products. A*02 is globally common, but A*0201 is at high frequencies in Northern Asia and North America. A2 is the most diverse serotype, showing diversity in Eastern Africa and Southwest Asia. While the frequency of A*0201 in Northern Asia is high, its diversity is limited to A*0201 the less common Asian variants A*0203, A*0206.

Serotype
The serotyping for the most abundant A*02 alleles is good. For A*0203, A*0206, A*0207 serotyping is borderline useful. There is a separate serotyping for A203 and A210. There are over 125 alleles identified (mostly by sequence homology) as being A2, of those 8 are nulls, and a large majority have unknown serotypes.

Disease Associations
A2 Associated with spontaneous abortion in A2+/A[other] phenotypic children

By haplotype
A*02:Cw*16 is associated with increased higher viral load in HIV

A2-B Haplotypes
A2-B7 (Node in Netherlands) A2-B5 A2-B8
 * A2-B51
 * A2-B52

A2-B13

A2-B14 A2-B15 A2-B16 A2-B18
 * A2-B64
 * A2-B65
 * A2-B62
 * A2-B63
 * A2-B70,71,75,76
 * A2-B46 (Node in Southern China, may be most abundant haplotype)
 * A2-B44
 * A2-B45

A2-B27

A2-B35

A2-B37 A2-B39 (Node in North American Amerinds)

A2-B40

A2-B46
 * A2-B60
 * A2-B61

A2-Cw5-B44
A2-Cw5-B44 is the multi-serotype designation for the haplotype HLA-A*0201:C*0501:B*4402, the class I portion, of an ancetral haplotype (A2-B44-DR4-DQ8). The full haplotype is (for relative distances see Human leukocyte antigens:

A*0201 : C*0501 : B*4402 : DRB1*0401 : DQA1*0301 : DQB1*0302

Another haplotype that is more common in Central Europe is the (A2-B44-DR7-DQ2)

A*0201 : C*0501 : B*4402 : DRB1*0701 : DQA1*0201 : DQB1*0202

Over northwestern Europe A2-B44 shows a single common ancestor which contributed the Cw5 allele to the haplotype. The haplotype appears to have been introduced early in European prehistoric period, frequencies of the haplotype generally correlate with A1-Cw7-B8 and A2-B7. The haplotype is considerably more equilibrated relative to A1-B8 and a possible reason is gene flow from iberia or the east with related haplotypes after initial migrations.