What if your own body hunted you?

You are a germ on the tip of a thorn, and the thorn just went into your own finger. Every stage, a new part of your immune system closes in: the clot, complement proteins, a macrophage that was already waiting, a swarm of neutrophils, a net made of DNA, the lymph node, and a storm of antibodies made just for you. You are Staphylococcus aureus, the germ behind most skin infections. The defences come in their real order. Complement proteins tag germs within minutes and punch holes in many kinds of bacteria, but staph's thick wall resists the holes, so it only gets marked. Most adults already carry antibodies to staph. Neutrophils swarm by signalling each other, and they can throw out their own DNA as a sticky net; staph makes an enzyme that cuts these nets. Dead neutrophils spill calprotectin, a protein that grabs the zinc and manganese staph needs. The lymph node finds the rare B cell that fits the germ and copies it; those copies make thousands of antibodies a second. Sizes are roughly to scale, except the antibodies, which are drawn far bigger than they are so you can see them. The video is much faster than real life: the clock in the corner shows roughly how long each step really takes (minutes for complement, hours for the swarm, about a week for new antibodies). "You" are really your line of copies; one germ would not live for a week. The copy counts are illustrative. A germ can't hear, so the heartbeat is the throb you'd feel in a sore finger. About 3 in 10 people carry staph on their skin or in their nose right now, and their body keeps it there. If a cut gets a red streak going up the arm, or you get a high fever, see a doctor. 0:00 The thorn 0:34 The flood 1:04 Tagged 1:34 The sentry 2:06 The wall opens 2:36 The swarm 3:12 The net 3:42 Up the arm 4:14 The lymph node 4:48 Antibodies 5:18 The last hunter 5:56 Your finger #whatif #immunesystem #biology #humanbody #science