HLA-A

HLA-A is a major histocompatibility complex (MHC) class I molecule, encoded by the HLA-A gene. It is a human leukocyte antigen, a protein that plays a crucial role in the immune system. HLA-A is part of the HLA class I heavy chain paralogues. This group also includes HLA-B and HLA-C. The HLA-A molecule is a heterodimer consisting of a heavy chain and a light chain (beta-2 microglobulin). The heavy chain is approximately 45 kDa and its gene contains 8 exons. The heavy chain is anchored in the membrane. For HLA-A, the alpha chain has 365 amino acids. The alpha chain is produced by 2750 nucleotides long mRNA. The alpha chain has the following protein sequence.

Function

HLA-A is a cell surface protein that interacts with killer cell immunoglobulin-like receptors (KIR) found on natural killer cells, which are a component of the innate immune system. HLA-A presents small peptides derived from intracellular proteins to the immune system. This presentation allows the immune system to detect cells that are infected with viruses or other pathogens.

Polymorphism

HLA-A is highly polymorphic, meaning that it has many different alleles, each of which produces a slightly different protein. This polymorphism allows the immune system to respond to a wide range of foreign invaders. The HLA-A locus has over 1000 known alleles.

Clinical significance

HLA-A alleles have been linked to a variety of diseases, including ankylosing spondylitis, Behcet's disease, and certain types of cancer. They are also important in organ transplantation, as matching the HLA-A alleles of the donor and recipient can reduce the risk of graft-versus-host disease.

See also

• HLA-B
• HLA-C
• Major histocompatibility complex
• Human leukocyte antigen

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HLA-A

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  Illustration HLA-A
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  Peptide Loading Complex