Your body deliberately kills billions of its own cells every single day
An average adult loses somewhere between 50 and 70 billion cells a day to apoptosis, a tidy, genetically controlled form of self-destruction. It is not damage. Your fingers exist because the cells that once webbed them together in the womb were programmed to die on schedule.
Apoptosis differs sharply from necrosis, the messy death caused by injury. A dying cell shrinks, bulges into blisters, condenses and chops up its DNA, then breaks into neat packages called apoptotic bodies that scavenger cells swallow before any contents can leak and harm the neighbours. Children aged 8 to 14 shed roughly 20 to 30 billion cells daily this way.
Because the process cannot be reversed once started, the trigger is tightly controlled. In the intrinsic route, a stressed cell decides to die itself, a decision that depends on proteins escaping from its mitochondria, such as cytochrome c released with the help of Bax and Bak. In the extrinsic route, other cells deliver the order by binding to death receptors on the surface. Either way, initiator enzymes called caspases switch on executioner caspases, which shred proteins indiscriminately.
Balance matters for health. Too much apoptosis wastes tissue away, while too little lets cells multiply unchecked, as in cancer. The field took off in 1988, when BCL2, the gene behind follicular lymphoma, was shown to make a protein that blocks cell death, and the 2002 Nobel Prize went to John Sulston, Sydney Brenner and H. Robert Horvitz for tracing the controlling genes in the tiny worm C. elegans.
Carl Vogt described the principle in 1842, but it lay forgotten until John Kerr in Queensland spotted it under the electron microscope in 1965. With Alastair Currie and Andrew Wyllie at Aberdeen he named it in 1972, borrowing a word suggested by Greek professor James Cormack for leaves dropping from a tree, and argued the second p should be silent.
Source: Apoptosis
