Figure 1.

Features of cells undergoing apoptosis, pyroptosis or secondary necrosis. Apoptosis is orchestrated by the executioner caspases 3 and 7 which are activated by the apoptosome or death receptor ligation. Cells undergoing apoptosis are characterized by their defining blebs around the plasma membrane, cellular shrinkage, fragmentation into apoptotic bodies, nuclear condensation, and mitochondrial outer membrane permeabilization. Pyroptosis is orchestrated by cleavage of GSDMD by inflammatory caspases 1 and 11 within the inflammasome complexes, whereas secondary necrosis is orchestrated by cleavage of GSDME by caspase-3 during apoptosis. Cells undergoing pyroptosis/secondary necrosis exhibit permeabilized plasma and organelle membranes, cellular swelling, and release of intracellular contents through the GSDMD or GSDME pores. These cells, unlike apoptotic cells, do not maintain their plasma membrane integrity.