Apoptosis is a regulated, energy-dependent process by which a cell se- destructs. This mechanism of programmed cell death plays an important role in normal development and control of cell numbers in mature a- mals. Apoptosis was initially defined by morphological criteria to describe the distinctive appearance of dying cells that developed nuclear conden- tion, cell shrinkage, and cytoplasmic blebbing. Initiation of the apoptotic process can come from external or internal stimuli and is highly regulated both by molecules that facilitate and by molecules that inhibit the process. Common features of apoptosis include activation of proteases and - cleases, mitochondrial membrane permeabilization, chromatin disruption, and translocation of phosphatidylserine from the inner to the outer s- face of the plasma membrane. Apoptotic cells attract phagocytes that - gulf the apoptotic bodies and prevent tissue damage in the region. Intense investigation of the cell death process has defined many molecular features of the pathway by which regulation and execution can be exploited by pathogens.
