“You could look at it and conclude that it’s crazy that the immune system attacks itself,” says Davis. “Alternatively, once you start to think about all that the immune system has to do, it’s surprising that it doesn’t happen all the time. Your immune system is constantly bombarded by things it has never seen before, things that may have only just come into existence—like new flu viruses, which are constantly mutating into new forms. So your immune system has to be able to identify and fight off a more or less infinite number of things.”
