The classic medical standoff we all dread. Your immune system, programmed to attack anything it doesn't recognize, spots that new transplanted organ and thinks, "Fresh intruder detected. Must eliminate." Meanwhile, the transplanted organ is just standing there nervously like, "I'm just trying to help keep this body alive, please don't shoot." And this, friends, is why transplant patients take immunosuppressants—to convince the overzealous security guard that is their immune system to chill out and accept the new roommate.