Nothing explains the immune system as eloquently as the anime show “Cells at Work!“. This Japanese anime anthropomorphizes cells and breaks down the interwoven complexities of the immune system into relatable characters with captivating story arcs. The immune cells are the protagonists composed of divisions stationed around the body, ready to defend it. The main antagonists are bacteria, viruses, and self-cancer cells attempting to invade and take over. In this show, art imitates life, and no character is as bad *** as the natural killer (NK) cell.
Ninjas or Shinobis were assassins trained in the art of ninjutsu for warfare in medieval Japan. They were nimble athletes skilled at espionage and, of course, killing. When it comes to our body’s defence, NK cells are the ninjas of the immune system and share many characteristics.
They are agile, nimble and barriers don’t stop them
Ninjas were extremely agile athletes, frequently needing to jump across moats, scale walls and infiltrate without being seen. Likewise, immune cells need to get to the invasion site to stop an assailant. While many immune cells are restricted to locations within the body and require great help and guidance to reach those sites, NK cells do not. Instead, NK cells are found all over the body and can quickly move from the blood into tissues and through tissues themselves.
They are elusive forward scouts skilled at espionage
Ninjas were elusive and made up a tiny percentage of the army. They had highly specialized tasks, including being sent into enemy encampments to conduct espionage, assassinate, or cause as much disruption as possible to disorganize defences against an incoming assault. NK cells are much of the same. They make up just 2% of the blood’s white blood cells yet have critical roles in determining how our bodies will respond to an attack. NK cells are one of the first to arrive at a site of infection, and their response can dictate what immune cells are required after that. They do this by assessing the environment and releasing signals called cytokines. These cytokine messages are specialized instructions to inform other immune cells how to react.
They are killers
Ninjas were skilled killers with an arsenal of weapons at their disposal. While famously depicted with their katanas and throwing stars, ninjas were skilled at mixing poisons and making medicine. NK cells were named for their similar affinity to killing. They can assassinate their targets using receptor katanas that bind to an assailant resulting in their death. Their throwing stars come in the form of perforin, a pore-forming protein that essentially rips holes in the membrane of the target. They also mix poisons, named granzymes, to deliver to target cells leading to death.
The most exciting thing about NK ninja cells is their potential use as therapies. Natural killer cell-based immunotherapies are currently being tested as therapies for everything from cancer to COVID-19.
Comic illustration by Sarah Nersesian