Cancer cell death. Coloured Scanning Electron Micrograph (SEM) of killer T-lymphocytes (orange) beginning to attack a cancer cell (mauve). These lymphocytes will kill the cancer cell by chemically inducing Programmed Cell Death (PCD, also known as apoptosis). Killer T- lymphocytes are part of the body's immune response system. They are programmed to seek out, attach themselves and kill cancer cells, usually using chemicals. In this case the lymphocytes have released a chemical which specifically induces apoptosis in the cancer cell. Apoptosis is a natural method of cell death which is being used as a potential treatment for cancer.