Apoptosis (or programmed cell death) is a central feature of normal tissue development in the fetus and of cell replacement in certain adult tissues (e.g., the thymus).¹ In contrast to necrosis (or accidental cell death), apoptosis is a tightly regulated series of energy-dependent molecular and biochemical events orchestrated by a genetic program. Cells undergoing apoptosis can be distinguished from those undergoing necrosis by several characteristic features, including blebbing of the cell membrane, a reduction in cell volume, and condensation of nuclear chromatin. In contrast to necrosis, apoptosis usually occurs in isolated cells without inflammation.

For a single cell, the process . . .