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.

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