In a dramatic video, scientists show the behavior of cytotoxic T cells in our body as they hunt down and destroy cancer cells before moving on to their next target.
"Inside all of us lurks an army of serial killers whose primary function is to kill, and then kill again," says the video's narrator, Professor Gillian Griffiths, director of the Cambridge Institute for Medical Research in England.
These "serial killers" that hunt around in our body may sound like the stuff of science fiction, but they are very real immune system cells.
Cytotoxic T cells patrol our bodies with remarkable precision and efficiency as they seek out and annihilate cells that are cancerous or infected with dangerous viruses.
There are billions of these cellular assassins that are each about a tenth of the width of a human hair, and they move rapidly around their environment, looking out for "markers" on the surface of various cells to see if there are any abnormal or foreign molecules.
If they spot an intruder, they lock onto their target and kill them by injecting them with poisonous molecules called cytotoxins.
This incredible process was captured on film by researchers from the University of Cambridge, and the video was part of a study that was published in the journal Immunity.
[Image via Gillian Griffiths / Jonny Settle / Cambridge University]