What is the role of the major histocompatibility complex (MHC) in the pathophysiology of human leukocyte antigen (HLA) system?

Updated: Oct 30, 2018
  • Author: Anna Luisa Di Lorenzo, MBBCh; Chief Editor: Andrew A Dahl, MD, FACS  more...
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Three classes of gene products are encoded within the small region of the major histocompatibility complex (MHC). This group of genes code for proteins found on the surfaces of cells that help the immune system recognize foreign substances. Class I MHC molecules include HLA-A, HLA-B, or HLA-C and serve as the antigen-presenting platform for CD8 or suppressor T cells. Class I molecules are present on all nucleated cells. Class II MHC molecules, the HLA-D region, serve as the antigen-presenting cells for CD4 or helper T cells. Macrophages and dendritic cells are the important class II antigen-presenting cells. Class I and class II molecules allow antigen presentation to the specific T-cell receptor via a specific structural groove in its tertiary structure. Class III MHC molecules include several proteins with other immune functions, such as cytokines, heat shock proteins, and parts of complement system. Although all three classes have loci clustered on chromosome 6, the gene location of the third class is a result of translocation during evolution.

Autoimmune/inflammatory conditions can occur if mutations in the groove binding site of class I and II molecules occur, leading to inappropriate binding to self-peptides or certain environmental peptides.

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