HLA-A9

HLA-A9 is a human leukocyte antigen serotype within HLA-A serotype group. The serotype is determined by the antibody recognition of α9 subset of HLA-A α-chains. For HLA-A9, the alpha chain is encoded by *HLA-A*23 and *HLA-A*24 gene alleles.

Structure and Function

HLA-A9 is a cell surface protein that plays a crucial role in the regulation of the immune system in humans. It is part of 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 approximately 45 kDa and its gene contains 8 exons. Exon one 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.

Clinical Significance

HLA-A9 has been associated with a number of diseases, including rheumatoid arthritis, type 1 diabetes, and celiac disease. It is also implicated in the rejection of organ transplants.

See Also

• HLA-A
• HLA-B
• HLA-C
• HLA-D
• HLA-E
• HLA-F
• HLA-G