Hla

HLA is an acronym for "human leukocyte antigen". HLA antigens are also referred to as MHC antigens (more correctly, the term MHC should only be used for the mouse, where this term was coined).

HLA antigens are encoded by the HLA gene complex which in humans is located on the short arm of chromosome 6. Class I HLA antigens are expressed on the surface of all nucleated cells of vertebrates. Class I HLA antigens are expressed by certain immunologically active cells.

Both the HLA I and the HLA II gene complex exhibit a large allelic polymorphism, which is particularly pronounced in the area of the peptide binding sites. The different alleles result in an enormous variety of encoded HLA proteins. Together with the diversity of T-cell receptor specificities, this contributes to an almost unlimited diversity of adaptive immune responses.