Mouse anti-Guinea Pig CD8 monoclonal antibody for IHC, FC. CD8 is a 68 kDa disulphide-linked, transmembrane glycoprotein. The CD8 molecule serves as a receptor for MHC class I molecules and can mediate a function as a coreceptor in TCR-ligand binding and T-cell activation. Its cytoplasmic part is associated with the p56lck tyrosine kinase. CD8 is expressed by the great majority of cortical thymocytes and approximately 30% of medullary thymocytes, and by class I major histocompatibility complex restricted, mature suppressor/cytotoxic T cells. In addition a proportion of ?? T cells and NK cells express CD8. Thus, CD8 is expressed by about 25-35% of peripheral T cells, and about 30% of NK cells express low levels of CD8. Immunophenotyping of lymphocytes is widely applied as a component of the testing of peripheral blood for diagnosis of immunodeficiencies such as aquired immunodeficiency syndrome (AIDS). An increase in the percentage of CD8-positive T cells has been reported during cytomegalovirus infection.