One of the ironies of our modern lifestyle is that some of our most worrisome ailments are autoimmune diseases, like lupus, multiple sclerosis, or Crohn’s disease. In these cases, as with allergies, we would rather have less robust immune response. It is thought that even heart disease is really a problem of out-of-control inflammation. Contrast this with the vast majority of human history (and developing countries today), in which infectious disease are of primary concern, and a more active immune system was a boon, rather than a liability. In addition, some of our most promising medical treatments, like implantable sensors, or even organ transplants, are greatly hindered by natural processes like biofouling and host-vs-graft responses. The ability to selectively turn off the immune response, without generally decreasing its effectiveness against actual pathogens, would be very valuable. A recent paper shows a possible method that uses the body’s own “self-recognition” protein. This is a very promising approach, since the immune system must have an innate mechanism to distinguish “self” from “invader,” and it appears that these researchers have been able to crack that system.