Our bodies go to great lengths to maintain "immune tolerance" to our cells and tissues. So what exactly is it? Simply, it is when the immune system ignores, or fails to react to a protein, cell or tissue in our body. When immune cells are developing, they are taught to tell the difference between things that are part of our own body and things that come from the outside. This way, our own cells and tissues are left alone, while things like viruses and bacteria that pose a threat to our health can be properly dealt with. But there are many ways that the immune system can mess up.
Sometimes, it can mistakenly view a part of our own body as a foreign object. This is what causes "autoimmune diseases," such as type 1 diabetes, multiple sclerosis, lupus, rheumatoid arthritis and others. The result is that it attacks the body's own tissue, causing (usually) permanent damage. One of the goals of immune tolerance therapies, therefore, is to stop these mistaken autoimmune responses by reprogramming the immune system so that it once again attacks only real threats, but not the body's own cells or tissues.
Other times, the immune system may correctly identify something as foreign, however, it misjudges how much of a threat that it poses to our health. Allergies are one example. Allergies to harmless substances like grass and tree pollens cause a huge amount of discomfort to people all around the world; and allergies to foods like peanuts can turn deadly. In such conditions, the immune system overreacts, mobilizing a large part of its resources against only a very minor threat. Reprogramming the immune system to ignore these insignificant threats without compromising its ability to respond to real threats is the goal of immune tolerance therapy for allergic disease.
And finally, in exceptional circumstances, the immune system may be working just fine, but by doing so, it puts our health at risk. This is what happens when we transplant organs from one person to another. Rightly so, the immune system recognizes the cells, tissue or an organ from another individual as "foreign" and goes about its job trying to rid it from the body. What it doesn't know, is that organ transplants give life to thousands of individuals each year and are often the treatment of last resort. In this case, the goal is to teach the immune system to tolerate the transplanted organ, without attacking it.
So, simply put, the goal of "immune tolerance" research is to reprogram the immune system in very specific ways that correct problems that threaten our health. The important part about tolerance, however, is that it leaves the body's normal disease-fighting immune responses untouched, so that it can continue to perform its important role. Current immunosuppressive therapies do not do this - they compromise the ability of the immune system to respond to anything.
Clearly, treatments capable of producing tolerance would be remarkably powerful and find use in a many, many For instance, in psoriasis, we could teach the body to tolerate the skin cells; we could prevent the destruction of nerve cells that occurs in multiple sclerosis and we could prevent autoimmune responses that lead to rheumatoid arthritis, lupus, and many other devastating diseases. For allergies, the immune system could be trained to ignore allergens like pollen and cat dander. Similarly, asthma might be neutralized by the very same treatments. We might also teach the immune system to fully accept an organ or tissue that has been transplanted from another person.
