Fig. 4

Illustration of the relationships among apoptosis, SD, SICD and necrosis. It is the healthy but useless cells that undergo apoptosis, whereas it is the useful but damaged cells that die of SICD (either sIaLCD or SInLCD) or necrosis. Useful cells, either healthy or damaged ones, can age and eventually die of SD, but whether obsolete cells also undergo SD is an intriguing question that remains murky, because these cells may be removed much more efficiently via apoptosis. Apoptotic and SIaLCD cells will be phagocytosed whereas SInLCD and necrotic cells will decompose to cellular dregs that cause inflammation. Moreover, SInLCD resembles necrosis that will cause regeneration and wound healing, probably in association with scar formation, but these activities do not follow SIalCD and apoptosis