The human immune system can recognize and destroy foreign objects. In addition to bacteria and viruses, drug-delivering nanoparticles, implanted pacemakers, and artificial joints, which are also foreign, also trigger an immune response that causes drug failure, rejection, or inflammation. To this end, scientists at the University of Pennsylvania have developed a new method of attaching protein “passports” to these therapeutic devices so that they can pass through the body’s defense system. The body will reject the invading foreign objects without discrimination, which is caused by the body’s natural immune system. This process involves a variety of cells, such as macrophages, which can detect, swallow and destroy invaders; serum proteins will…