Immune: A Journey Into the Mysterious System That Keeps You Alive

by Philipp Dettmer

Your body is wrapped in an ingenious self-repairing border wall that is incredibly hard to pass and that protects you extremely efficiently. If it is breached, your Innate Immune System reacts immediately. First your black rhinos, Macrophages, huge cells that swallow enemies whole, appear and dish out death. If they sense too many enemies they use cytokines, information proteins to call your chimp-with-machine-gun Neutrophils, the crazy suicide warriors of the immune system. Neutrophils don’t live long and their fighting is harmful to the body because they kill civilian cells. Both of these cells cause inflammation, bringing in fluid and reinforcements to an infection, making a battlefield swell up. One of the reinforcements is complement proteins, an army of millions of tiny proteins that passively support the immune cells in their fight and help mark, attach to, maim, and clear enemies. These powerful teams together are enough for most small wounds and infections you encounter.

consequence the Macrophages guarding your intestines have two properties: Firstly, they are really good at swallowing bacteria. And secondly, they do not release the cytokines that call in Neutrophils and cause inflammation. They are more like silent killers, casually eating bacteria that cross the line but without making a fuss about it.

The main thing a virus needs to be able to do to thrive is to get inside cells. And for that they abuse a weak point of all cells that living things will never be able to completely protect against: They attack receptors.

a virus transfers its genetic material into its victim and forces the cell to stop making cell stuff. It is turned into a virus production machine.

A virus is smaller and somewhat harder to detect than bacteria because it doesn’t have a metabolism that releases garbage chemicals that can be picked up by immune cells. And it hides inside cells for most of its life cycle and tries to manipulate infected cells to trick the immune system to stand down. It can change much more quickly than bacteria and a single virus can turn into ten thousand within a day, turning on exponential growth rapidly.