Apoptosis vs Necrosis

Features of Apoptosis and Necrosis. Apoptosis is Programmed Cell Death (PCD) or "cellular suicide", necrosis involves stress induced swelling and lysis.

Morphological features

	Apoptosis (image)	Necrosis (image)
Outset	Shrinking of cytoplasm, condensation of nucleus.	Swelling of cytoplasm and mitochondria.
Plasma membrane	Blebbing of plasma membrane without loss of integrity	Loss of membrane integrity
Chromatin	Aggregation of chromatin at the nuclear membrane.
Organelles	Mitochondria become leaky due to pore formation involving proteins of the bcl-2 family.	Disintegration (swelling) of organelles
Vesicles	Formation of membrane bound vesicles (apoptotic bodies)	No vesicle formation, complete lysis
Terminal	Fragmentation of cell into smaller bodies	Total cell lysis

Biochemical features

	Apoptosis	Necrosis
Regulation	Tightly regulated process involving activation and enzymatic steps.	Loss of regulation of ion homeostasis.
Energy input	Energy (ATP)-dependent (active process, does not occur at 4°C)	No energy requirement (passive process, also occurs at 4°C)
DNA	Non-random mono- and oligonucleosomal length fragmentation of DNA (Ladder pattern after agarose gel electrophoresis)	Random digestion of DNA (smear of DNA after agarose gel electrophoresis)
Timing	Prelytic DNA fragmentation	Postlytic DNA fragmentation (= late event in cell death)
Biochemical events	Release of various factors (cytochrome C, AIF) into cytoplasm by mitochondria. Activation of caspase cascade. Alterations in membrane asymmetry (translocation of phosphatidylserine from the cytoplasmic to the extracellular side of the membrane)

Physiological impact

	Apoptosis	Necrosis
Extent	Localized effect that destroys individual cells.	Affects groups of contiguous cells.
Induction	Induced by physiological stimuli (lack of growthfactors, changes in hormonal environment).	Evoked by non-physiological disturbances (complement attack, lytic viruses, hypothermia, hypoxia, ischemica, metabolic poisons)
Phagocytosis	Phagocytosis by adjacent cells or macrophages.	Phagocytosis by macrophages
Immune system	No inflammatory response.	Significant inflammatory response.