Apoptosis Apoptosis Definition Apoptosis is programmed cell death, in which morphological nuclear changes and DNA fragmentation occur. The nuclear changes are nuclear blebbing to form micronuclei, and condensation of chromatin. Other features include loss of intercellular contact, vacuolation, and a relative conservation of cellular organelles. Necrosis, the other major type of cell death occurs as a result of cytoplasmic membrane damage, ion release and osmotic lysis with little nuclear or DNA damage until relatively late in the process.
Apoptosis is an essential part of growth, development and adaptation in multicellular organisms.
The coordinated, programmed death of cells in the fingerwebs, for example, is a necessary part of the separation of fingers during embryological development. Without programmed cell death, cell proliferation would lack an improtant component of control of oncogenic processes. Programmed death of phagocytic cells may be an important part of host defence against intracellular pathogens including Mycobacterium tuberculosis , in which apoptosis has been shown to be a more effective antibacterial strategy than necrosis. Finally, programmed death of cells allows clearance of cellular debris by phagocytes without release of potent proinflammatory mediators. Mechanisms of death One of the hallmarks of apoptosis is that the molecular machinery of death resides within the cell.