Cytokines produced by the T4-helper lymphocyte binds to receptors on the activated T8-lymphocyte enabling it to differentiate into a cytotocic T-lymphocyte (CTL). The CTLs contain granules that hold pore-forming proteins called perforins and proteolytic enzymes called granzymes in a protected state. When the TCR and CD8 of the CTL binds to the MHC-I/epitope on the surface of a target cell, this sends a signal that triggers the release of the perforins, granzymes, and chemokines.

The perforin molecules polymerize and form pores in the membrane of the infected cell. The pores, similar to those produced by MAC, increase the permeability of the infected cell and contribute to cell death. The perforin pores also allow granzymes to enter. Certain granzymes, in turn, can then activate the caspase enzymes that lead to apoptosis of the infected cell. The the caspases are proteases that destroy the protein structural scaffolding of the cell (the cytoskeleton) and degrade the cell's nucleoprotein.