Cancer cell death. Coloured Scanning Electron Micrograph (SEM) showing a killer T-lymphocyte (orange) inducing a cancer cell (mauve) to undergo Programmed Cell Death (PCD). Mauve vesicles, or apoptotic bodies emerging from the cancer cell indicate PCD (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 lymphocyte has 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.