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The human leukocyte antigen (HLA) system is a complex of genes on chromosome 6 in humans that encode cell-surface proteins responsible for regulation of the immune system. [1] The HLA system is also known as the human version of the major histocompatibility complex (MHC) found in many animals.
An HLA allele coding non-expressed gene is termed "Null Allele", for example: HLA-B*15:01:01:02N. The expression level can also detected by serotyping, an HLA gene coding for antigens which has low protein expression on the cell surface is termed "Low Expresser", for example: HLA-A*02:01:01:02L.
HLA-A is a group of human leukocyte antigens (HLA) that are encoded by the HLA-A locus, which is located at human chromosome 6p21.3. [1] HLA is a major histocompatibility complex (MHC) antigen specific to humans. HLA-A is one of three major types of human MHC class I transmembrane proteins. The others are HLA-B and HLA-C. [2]
The most diverse loci, namely HLA-A, HLA-B, and HLA-C, have roughly 6000, 7200, and 5800 known alleles, respectively. [39] Many HLA alleles are ancient, sometimes of closer homology to a chimpanzee MHC alleles than to some other human alleles of the same gene. MHC allelic diversity has challenged evolutionary biologists for explanation.
In genetics, a locus (pl.: loci) is a specific, fixed position on a chromosome where a particular gene or genetic marker is located. [1] Each chromosome carries many genes, with each gene occupying a different position or locus; in humans, the total number of protein-coding genes in a complete haploid set of 23 chromosomes is estimated at ...
The discovery of the MHC and role of histocompatibility in transplantation was a combined effort of many scientists in the 20th century. A genetic basis for transplantation rejection was proposed in a 1914 Nature paper by C.C. Little and Ernest Tyyzer, which showed that tumors transplanted between genetically identical mice grew normally, but tumors transplanted between non-identical mice were ...
HLA-C is a locus on chromosome 6, which encodes for many HLA-C alleles that are Class-I MHC receptors. HLA-C, localized proximal to the HLA-B locus, is located on the distal end of the HLA region. Most HLA-C:B haplotypes are in strong linkage disequilibrium and many are as ancient as the human species itself.
It is likely that human MHC class Ib loci (HLA-E, -F, and -G) as well as MHC class I pseudogenes arose from MHC class Ia loci (HLA-A, -B, and -C) in this birth-and-death process. [ 22 ] References