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26 March 2012

Cell Euthanasia

Apoptosis or programmed cell death is how multicellular organisms purposefully destroy and recycle their old, damaged or pre-cancerous cells. In human adults, roughly 70 billion cells are killed off every day through apoptosis. In this animation, a killer T cell — one of the foot soldiers of our bodies’ defence system — binds to the diseased cell using a special molecule or ligand. Akin to the Grim Reaper’s bony outstretched hand, the killer T cell’s death ligand triggers a cascade of chemical signals in the diseased cell which ultimately kills it. First, the diseased cell shrinks, and then breaks into small fragments, which are ‘eaten’ by other body cells. As well as being used to destroy damaged, malfunctioning cells, apoptosis also sculpts organs and tissue during development. Our fingers and toes are formed like gloves from mittens as cells apoptose between digits.

Written by Andrew Purcell

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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