HLA-A3

HLA-A3 (A3) is a human leukocyte antigen serotype within HLA-A serotype group. The serotype is determined by the antibody recognition of α³ subset of HLA-A α-chains. For A3, the alpha, "A", chain are encoded by the HLA-A*03 allele group and the β-chain are encoded by B2M locus. This group currently is dominated by A*0301. A3 and A*03 are almost synonymous in meaning. A3 is more common in Europe, it is part of the longest known multigene haplotype, A3-B7-DR15-DQ6.

Serotype

A3 is primarily composed of A*0301 and *0302 which serotype well with anti-A3 antibodies. There are 26 non-synonymous variants of A*03, 4 nulls, and 22 protein variants.

Associated diseases

A3 serotype is a secondary risk factor for myasthenia gravis and lower CD8⁺ levels in hemochromatosis patients. The HFE (Hemochromatosis) locus lies between A3 and B7 within the A3::DQ6 superhaplotype.

In HIV

HLA-A3 selects HIV evolution for a mutation Gag KK9 epitope and results in a rapid decline in the CD8 T-cell response. CD8 T-cells are responsible for quickly killing HIV infected CD4+ cells. This type of evolved response may not be specific for HLA-A3 and since HIV is capable of adapting quickly in situ to selective factors.