Apoptosis is a process of deliberate suicide by a cell in a multi-cellular organism. It is one of the main types of programmed cell death, and involves an orchestrated series of biochemical events leading to a characteristic cell morphology and death. The apoptotic process is executed in such a way as to safely dispose of cell corpses and fragments.
Apoptosis can occur when a cell is damaged beyond repair, infected with a virus, or undergoing stress conditions such as starvation. The tumor-suppressing gene p53 can also induce apoptosis via DNA damage or toxic chemicals.
The decision for apoptosis can come from the cell itself, from the surrounding tissue, or from a cell that is part of the immune system. Because of this connection with the immune system, apoptosis is studied in an extensive variety of diseases including HIV and cancer.