Implants and Our Immune Systems

An implant is an object used for either health or cosmetic purposes that is inserted inside the human body for a period of time. While implants can be physically or aesthetically pleasing, our immune systems think otherwise. They are designed to attack any foreign substance, such as bacteria, viruses, and parasites, and implants are no exception. While it is good that our immune systems can tackle, intercept, and destroy anything they believe should not be there, our immune systems treat helpful implants, like a prosthetic knee for instance, the way they would a harmful bacteria or virus. When an implant is placed in the body, its presence triggers a “foreign body response”. The process begins with free-floating proteins, such as antibodies, that stick themselves to the surface of the implant. As the antibodies attempt to neutralize the new object, they send out a signal that brings other cells to the site to strengthen the attack. Among the early-responding inflammatory cells are neutrophils and macrophages, which work to help breakdown and degrade the implant. If the cells are unable to degrade the implant, the macrophages quickly group together to form a mass of cells known as a “giant cell”. As this happens, another group of cells, called fibroblasts, travel to the site to deposit layers of dense connective tissue. Overtime, the connective tissue builds up, forming a scar around the implant. While our immune system might celebrate a victory for successfully stopping the foreign body, it is us who pay a hefty price in the end. The scar created by the immune system acts as an impassable wall, which may block vital interactions between the body and the implant. However, researchers are continually finding ways to trick the immune system into accepting the new devices and implants we put into our bodies. Some implants are coated with certain chemicals and drugs, which can weaken the immune response, and others are made out of natural materials and in ways that directly imitate the tissue, so the immune system isn’t as aggressive. If researchers continue to improve the implants we put into our bodies, it could open the door to a whole other world of medical discoveries and answers.