A T8-lymphocyte uses its TCR and CD8 to recognize a MHC-I molecule with attached peptide being presented by the APC. This interaction, along with secondary interactions such as B7, CD40, LFA-3, and ICAM-1 molecules on the APC binding to corresponding ligand molecules (CD28, CD40L, CD2, and LFA-1) on the naive T8-lymphocyte, results in activation of the T8-cell and its differentiation into an effector cell called a cytotoxic T-lymphocyte (CTL).