Major histocompatibility complex (MHC)

MHC

The most important histocompatibility antigens are encoded by genes clustered in a genetic region defined as the Major Histocompatibility Complex (MHC). The human MHC or the Human Leukocytes Antigen (HLA) region comprises about 4MB on chromosome 6 encoding for approximately two hundred genes, many of which are involved in immune response.

MHC genes in human encode for the HLA molecules

The MHC contains two classes of HLA genes: HLA class I (HLA-A, HLA-B, HLA-C), which encode for the class I molecules and HLA class II (HLA-DR, HLA-DQ, HLA-DP), which encode for the class II molecules respectively. Some genes located between the class I and class II genes encode proteins of the complement system and are refered to as class III genes. Read more...

Functions of HLA molecules

MHC-Tcell interaction

The primary immunological function of Major Histocompatibility Complex (MHC) molecules is to bind and "present" antigenic peptides on the surfaces of cells for recognition (binding) by the antigen-specific T cell receptors (TCR's) of T cells.
MHC class I and class II molecules activate different populations of T lymphocytes. CD8 on cytotoxic T cells binds to MHC class I while CD4 on T helper cells binds to MHC class II.

Polymorphism

HLA genes are the most polymorphic genes in the human genome and as a consequence, very few individuals express the same alleles (MHC- or HLA-matched).

Transplantation results are much better when the recipient and the donor are HLA-matched. To be able to select the best donor, the patient’s MHC alleles are determined by HLA typing before the transplantation. Read more...

Role of minor histocompatibility antigens (mHC)

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