Keratinocytes undergo apoptosis to form the temporary protective coat on the outer layer of skin. Sunburn and peeling of skin occur when ultra-violet light causes keratinocytes to undergo premature apoptosis. How apoptosis works on the cellular level is not well understood , but it is known to take about three hours to complete. The vast majority of the cells are in the G o , nonproliferating, phase of the cell cycle. A specific set of transcription factors is activated from the highly conserved Hox gene family in cells undergoing apoptosis.
Apoptosis begins with the shrinking of the nucleus and cytoplasm of the cell.
A good view of this is illustrated on the cover of the December 1996 issue of Scientific American . The subcellular fragments are then ingested by neighboring cells or macrophages. This all happens without any leakage of cell contents into the extra-cellular space or bloodstream. This is important because accidentally leaked cytoplasm would trigger an inflammatory response in the organism. Apoptosis is relatively inconspicuous to the immune system, whereas necrosis results in inflammation in the surrounding environment.