If you know how to drive a car, then you know how the immune system works, somewhat. Actually, you don’t even have to know how to drive. You just have to be familiar with the concept of an accelerator and brakes. Let’s think of anything that activates the immune system as the “accelerator” and whatever suppresses the immune system as the “brakes.” Would you want to drive a Lamborghini without working brakes? Unfortunately, some people live through life with the “brakes” of their immune system disabled. Do you know someone with rheumatoid arthritis, multiple sclerosis, lups, or inflammatory bowel disease (Crohn’s disease or ulcerative colitis)? These are autoimmune diseases in which the immune system is attacking various part of self. The “accelerator” of our immune system is what kicks in and eradicates a viral or bacterial infection. An immune system without an accelerator would be like a vehicle stuck on the railroad tracks of a fast approaching freight train without an accelerator or gas pedal. Well what about cancer? Cancer causes the accelerator to be stepped on a little (which is good), but at the same time, it causes the brakes to be stepped on a lot, with both feet! In 2011, ipilimumab was the first FDA-approved drug that works by taking the “foot off the brakes ,” so to speak, of the immune system. In some patients with cancer, the drug can result in rapid eradication of the cancer. Not surprisingly, a potential side effect of the drug is self-attack of the immune system against the colon and other parts of the body. You might think, “I wouldn’t mind exchanging widely metastatic cancer for a “little” autoimmune disease.” But cancer patients have been known to die from an overly active immue system that couldn’t be reined in.