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Major histocompatibility complex class I

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Definition

noun

A class of major histocompatibility complex wherein the histocompatibility antigens are expressed on the surface of essentially all cells except for red blood cells of jawed vertebrates, and are then recognized by CD8 co-receptors of cytotoxic T lymphocyte


Supplement

Major histocompatibility complex (acronym: MHC) refers to a cluster of genes that specify for major histocompatibility antigens expressed on the surface of the cell. In essence, epitopes (a fragment of protein that the cell displays on its surface) serve as MHC molecules that the immune cells use to distinguish self from non-self and then immunologically respond accordingly. MHCs are of three classes: MHC class I, MHC class II, and MHC class III.

Major histocompatibility complex class I (MHC class I) is the class of MHC that expresses MHC molecules (antigens) that are heterodimers. The antigen would be comprised of two polypeptide chains: α and β2-microglobulin.

MHC class I antigen is recognizable only by the CD8 co-receptor (compare: MHC class II). In particular, a cytotoxic T lymphocyte expresses CD8 receptor, which would dock to MHC class I antigen on the antigen-presenting cell. The interaction between the MHC class I antigen and the cytotoxic T lymphocyte causes the cytotoxic T lymphocyte to prompt the cell to undergo apoptosis. Thus, MHC class I promotes cellular immunity against intracellular pathogens (i.e. pathogens inside the host cell).

MHC class I antigens are found on all nucleated cells as well as on platelets of jawed vertebrates. Basically, all cells would express MHC class I antigens except for red blood cells.

In humans, MHC class I includes HLA-A, HLA-B, and HLA-C.


Abbreviation/Acronym:

  • MHC class I

See also: