HLA-A (Major Histocompatibility Complex, Class I, A) is a Protein Coding gene. Diseases associated with HLA-A include Hypersensitivity Syndrome, Carbamazepine-Induced and Hla-A-Related Altered Drug Metabolism. Among its related pathways are Allograft rejection and Immunoregulatory interactions between a Lymphoid and a non-Lymphoid cell. GO annotations related to this gene include poly(A) RNA binding and peptide antigen binding. An important paralog of this gene is HLA-B.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.