HLA-A屬于HLA I類重鏈相似度。這一類分子是由重鏈和輕鏈（β-2微球蛋白）組成的異二聚體。重鏈錨定在膜上。I類分子通過呈現內質網腔中的肽在免疫系統中起著中心作用。幾乎在所有細胞中都有表達。重鏈約45kDa，其基因包含8個外顯子。外顯子1編碼先導肽，外顯子2和3編碼α1和α2結構域，兩者結合肽，外顯子4編碼α3結構域，外顯子5編碼跨膜區，外顯子6和7編碼胞質尾。外顯子2和外顯子3內的多態性負責每一類1分子的肽結合特異性。這些多態性的分型通常用于骨髓和腎移植。已經描述了100多個HLA-A等位基因。
HLA-A belongs to the HLA class I heavy chain paralogues. This class I molecule is a heterodimer consisting of a heavy chain and a light chain (beta-2 microglobulin). The heavy chain is anchored in the membrane. Class I molecules play a central role in the immune system by presenting peptides derived from the endoplasmic reticulum lumen. They are expressed in nearly all cells. The heavy chain is approximately 45 kDa and its gene contains 8 exons. Exon 1 encodes the leader peptide, exons 2 and 3 encode the alpha1 and alpha2 domains, which both bind the peptide, exon 4 encodes the alpha3 domain, exon 5 encodes the transmembrane region, and exons 6 and 7 encode the cytoplasmic tail. Polymorphisms within exon 2 and exon 3 are responsible for the peptide binding specificity of each class one molecule. Typing for these polymorphisms is routinely done for bone marrow and kidney transplantation. Hundreds of HLA-A alleles have been described.