Genetics, Histocompatibility Antigen

Excerpt

Genetically encoded molecules, known as major histocompatibility complex (MHC) molecules or human leukocyte antigens (HLA), determine an individual’s ability to produce an immune response to different antigens. These MHC molecules are responsible for determining if a molecule is histocompatible with the individual and for initiating an immune response if it is deemed foreign. They are found in all nucleated cells and primarily function in antigen presentation to T cells. For an antigen presenting cell (APC) and a T cell to interact and initiate an immune response, the T cell must bind to the APC as well as the antigen bound to an MHC molecule. A major histocompatibility complex is a set of genes that code these MHC molecules/HLA antigens. Multiple genes code for different parts of the molecules and several possible combinations of gene products exist. As a result, the chance of two individuals expressing identical MHC molecules is tremendously low. Clinically, MHC molecules are significant as they are the principle mediators involved in transplant rejection.