Necrosis vs Apoptosis

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"apoptosis"[MeSH Terms] AND "necrosis"[MeSH Terms]

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apoptosis versus necrosis comparison morphology

This diagnostic comparison chart displays cytomorphological images of A549 (human lung adenocarcinoma) and BEAS-2B (human bronchial epithelial) cell lines following a 24-hour MTT assay. The grid compares the effects of biogenic silver nanoparticles (F-AgNPs) and Methotrexate (MTX) at varying concentrations (IC25, IC50, IC75) against untreated controls (A, H). Panels A–G illustrate A549 cells, where untreated controls (A) show high confluence and typical epithelial morphology. Treatment with F-AgNPs (B–D) and MTX (E–G) reveals dose-dependent cytotoxicity characterized by reduced cell density, cytoplasmic condensation, cell aggregation, and increased cellular debris, suggesting apoptosis and necrosis. Panels H–N depict BEAS-2B cells. Notably, F-AgNPs-treated BEAS-2B cells (I–K) maintain normal morphology and density similar to the control (H), indicating selective biocompatibility. In contrast, MTX-treated BEAS-2B cells (L–N) exhibit significant morphological degradation and proliferation inhibition. This comparative visual demonstrates the differential cytotoxic potential of silver nanoparticles versus conventional chemotherapeutics across malignant and non-malignant pulmonary cell lines.

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Necrosis vs apoptosis

Short version: Apoptosis is regulated, energy-dependent cell suicide that causes little or no inflammation. Necrosis is passive cell death after injury, with membrane rupture and intense inflammation.

Definitions

Necrosis: cell or tissue death, typically from factors external to the cell, with cell swelling, inflammation and eventual disappearance of cells (Bailey and Love's Short Practice of Surgery, 28th Ed, Ch. 11).
Apoptosis: programmed cell death driven by internal signals. It shows histologically as cell shrinkage and nuclear chromatin condensation (Bailey and Love's Short Practice of Surgery, 28th Ed, Ch. 11).

Comparison table

This follows Table 6.1 in Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol 1, p. 109.

Feature	Apoptosis	Necrosis
Occurrence	Physiological or pathological	Always pathological
Trigger	Range of extracellular and intracellular factors	Direct injury, anoxia
Distribution	Isolated single cells scattered through tissue	Groups of cells or whole areas of tissue
Mechanism	Active, ATP-dependent, regulated	Passive, regulation lost
Cell size and membrane	Cytoplasmic shrinkage; membrane blebs into apoptotic bodies	Swelling; membrane ruptures and contents spill out
Organelles	Preserved within apoptotic bodies	Lost
Nucleus	Endonuclease activation cuts DNA into oligonucleosomal fragments; chromatin condenses into crescents	Random DNA digestion; chromatin flocculates
Effect on surrounding tissue	Little or none	Intense inflammation

Additional points from general pathology knowledge

These come from my own knowledge, not the retrieved textbook passages.

Pathways of apoptosis:
- The intrinsic (mitochondrial) pathway is controlled by BCL-2 family proteins. Cytochrome c release activates caspase-9.
- The extrinsic (death receptor) pathway uses Fas or TNF receptors and activates caspase-8.
- Both pathways converge on executioner caspases (3, 6, 7).
- p53 triggers apoptosis after DNA damage.
Apoptotic cell clearance: phosphatidylserine flips to the outer membrane leaflet. Macrophages then phagocytose the cell without inflammation.
Why necrosis causes inflammation: leaked intracellular contents act as damage-associated molecular patterns (DAMPs). They attract neutrophils and macrophages.
DNA gel pattern: apoptosis gives a "ladder" of fragments. Necrosis gives a smear.
Examples of apoptosis:
- Embryogenesis, such as interdigital webbing.
- Hormone-dependent involution.
- Deletion of autoreactive lymphocytes.
- Cytotoxic T-cell killing.
- Viral hepatitis, where Councilman bodies form.
Examples of necrosis:
- Coagulative: infarcts, except in the brain.
- Liquefactive: brain infarcts and abscesses.
- Caseous: tuberculosis. Bailey and Love's Figure 11.20 shows a necrotic granuloma suggesting TB.
- Fat necrosis.
- Fibrinoid necrosis.
- Gangrenous necrosis.
They can coexist: in noise-induced hearing loss, outer hair cells show apoptotic change (nuclear condensation, shrinkage) at 5 minutes and necrotic change (nuclear swelling) at 30 minutes (Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol 2, section "Apoptosis and necrosis"). Severe or prolonged injury can push a cell from apoptosis to necrosis.
Necroptosis: this is regulated necrosis, mediated by RIPK1, RIPK3 and MLKL. It is morphologically necrotic but genetically programmed.

Exam mnemonic

Apoptosis: shrinks, single cells, ATP needed, caspases, no inflammation.
Necrosis: swells, sheets of cells, passive, ruptures, inflammation.

Recent literature check

A PubMed search of the last 2 years for systematic reviews and meta-analyses found nothing that changes these basic distinctions. The results were disease-specific, such as necroptosis in pancreatic cancer and nasal necrosis etiologies.

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