The Foreign Body Response: What Is It?
The human body is a complicated piece of machinery. Scientists have been trying to gain insight into its functions for centuries, and yet we still don’t know everything about it. Each part of the machine is equally complicated and works in sync with the rest of the body. One main part of this machine is the immune system, which works to protect the body from foreign materials in an attempt to prevent disease. Some of these materials can include implants or pathogens. The area of resistance to implants is a particularly interesting one that many scientists are still exploring because of its potential to revolutionize the feel of biomedical engineering.
The study of implants is a diverse and varied field, ranging from breast implants to prosthetics, to glucose monitors for people with diabetes. They are all made up of different biomaterials, in different shapes, sizes, and structures, but they all also have one thing in common. None can stay in the body permanently. The human body has evolved a response to implants such that it protects the body from both splinters and heart monitors in the same way: the Foreign Body Response.
The first thing that happens when an implant is injected into the body is it gains a layer of proteins on its surface, and inflammation occurs around it to isolate it from the rest of the body. After that, a type of cell called a macrophage binds to the surface of the implant and fuses with other macrophages to form foreign body giant cells that surround the implant, many times destroying it by releasing enzymes that are used to destroy splinters in the body. Next, the macrophages and giant cells use the process of phagocytosis to attempt to “consume” the foreign object. Most of the time, it is too big, however, so they bring other cells to the area to help them. These cells perform the fifth step, which is creating a capsule of tissue around the implant, creating a bubble that fully isolates it from the rest of the body and renders it useless.
The fact that scientists have been able to hold off the Foreign Body Response for anywhere from ten to twenty years in the human body is a miracle of science that we are still improving upon. Currently, doctors will have to remove and replace the implant from the body because it is now sitting useless in the body. The longest-lasting implants in the human body are breast implants, which can last anywhere from ten to twenty years before they must be replaced. Scientists in multiple companies are working to reduce or eliminate the foreign body response when it comes to other types of implants, and have had varying success. For example, some scientists have been using cancer tissues on rats in order to get their immune systems to ignore transplanted limbs on the rats. Nothing is perfect, and this is still an emerging field, but the possibilities are limitless. Making the nanobiomaterials is easy — conquering the Foreign Body Response? That’s the challenge.
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