CD8 T cell proliferates, followed by differentiation into CTL effector cells or CD8 T memory cells. Activated CTL forms a conjugate with the target cell. CTL rearranges cytoplasmic granules to direct them towards the target. CTL releases granule contents towards the target. Perforin monomers polymerize to form pores in the target cell membrane.
Water enters the target cell and ions leak out through the pores, resulting in target cell lysis.
CTL move on to next target. The exact origin of NK cells is unclear, although most researchers believe them to be derived from the lymphocyte lineage in the bone marrow. NK cells have some properties of Ly, but lack other important Ly characteristics. Most importantly, NK cells have no specific receptor for Ag and do not produce memory cells. NK cells lack cell surface expression of CD3.