Medical Definition of CD8
: a glycoprotein found especially on the surface of cytotoxic T cells that usually functions to facilitate recognition by cytotoxic T cell receptors of antigens complexed with molecules of a class that are found on the surface of most nucleated cells and are the product of genes of the major histocompatibility complex
Seen and Heard
What made you want to look up CD8? Please tell us where you read or heard it (including the quote, if possible).