CD8 T cells are T cells that carry the co-receptor CD8. They recognize antigens, for example viral antigens, that are synthesized in the cytoplasm of a cell. Peptides derived from these antigens are transported by TAP, assembled with MHC class I molecules in the endoplasmic reticulum, and displayed as peptide:MHC class I complexes on the cell surface. CD8 T cells differentiate into cytotoxic CD8 T cells.