The CD8 ?-chain (CD8a) is a transmembrane glycoprotein that exists as a homodimer, CD8??, or heterodimer with the CD8 ?-chain (CD8b), CD8??, to form the T cell receptor (TCR) co-receptor CD8.{53531,58323} CD8a is composed of an extracellular immunoglobulin variable-like (IgV) domain, which interacts with MHC class I molecules, a transmembrane domain, and a cytoplasmic tail that associates with the tyrosine kinase p56Ick and mediates signal transduction.{53531,58321,58323} CD8?? is expressed by cytotoxic T lymphocytes (CTLs), where it acts as a TCR co-receptor by enhancing T cell signaling and activation upon binding to antigen-displaying MHC class I molecules.{58322,58323} CD8?? is expressed by CTLs and intestinal epithelial lymphocytes, as well as ?? T, natural killer (NK), and dendritic cells, where it acts as a positive or negative regulator of cell activation in a cell-dependent manner. Cd8a-/- mice infected with M. tuberculosis exhibit reduced survival.{58324} Cayman's CD8a Polyclonal Antibody can be used for ELISA, immunocytochemistry (ICC), immunofluorescence (IF), and immunohistochemistry (IHC; paraffin) applications.