Cd8

Cd8 (Cluster of Differentiation 8) is a transmembrane protein that is primarily found on the surface of cytotoxic T cells and natural killer cells. It is also known as CD8a. The function of CD8 is to bind to the MHC class I molecule on the surface of infected cells and other host cells, which allows for the identification and destruction of these cells by the immune system.

CD8 was first identified in 1979 by two independent research groups. The first group, led by Professors schlossman and June, used monoclonal antibodies to show that a population of T lymphocytes could be distinguished from other populations based on their cell-surface expression of a novel glycoprotein antigen they termed “T3”. The second group, working under the direction of immunologist Avram Goldstein, purified this same glycoprotein from thymocytes and christened it “leu-2a”. Subsequent studies determined that leu-2a/T3 was indeed encoded by a single gene located on chromosome 2p11, which was subsequently named “cd8”.

The cd8 gene encodes for four different proteins: alpha, beta, gamma and delta subunits. These subunits are differentially expressed depending on the developmental stage of the cell; for example, alpha and beta subunits are expressed in mature T cells while gamma and delta are predominantly found in immature thymocytes. All four subunits are required for proper protein function; however, it is believed that the primary binding site for MHC class I molecules resides within the extracellular domain of the alpha chain .
The human cd8 gene has been shown to be under strong evolutionary pressure , likely due to its role in mediating immunity against pathogenic microorganisms . In fact, recent studies have shown that loss-of-function mutations in cd8 are associated with increased susceptibility to viral infections .