| αβ heterodimer|
| transmembrane receptor/ligand|
HLA-A31 (A31) is a human leukocyte antigen serotype within HLA-A serotype group. The serotype is determined by the antibody recognition of α31 subset of HLA-A α-chains. For A31, the alpha "A" chain are encoded by the HLA-A*31 allele group and the β-chain are encoded by B2M locus. This group currently is dominated by A*3101. A31 and A*31 are almost synonymous in meaning. A31 is a split antigen of the broad antigen serotype A19. A31 is a sister serotype of A29, A30, A32, A33, and A74.
A31 is more common in South and Central America.
There is substantive false reaction of A30 with A*3101, otherwise serological identification is good.
Examination of A31 haplotypes reveals a probable connection across northern Eurasia during the prehistoric period. Frequencies of the more 'tale-tell' haplotypes (A31-B60, B61, and B62) fall from NE to SW Europe. Other haplotypes appears to have spread from the Middle East (A31-B51 and A31-B35).