What the Body KnowsA leading scientist's guide to the way our immune system protects usbut only most of the time What is our immune system, and how does it work? A vast array of cells, proteins, and chemicals spring into action whenever our bodies are damaged, but immunity is not something you can see, touch, or feel. It can fight off malicious bacteria and viruses, locate cancerous growths, and even rewire our brainsbut sometimes our own tissues can get caught in its