Immune tolerance, or immunological tolerance, is when the immune system does not react to a substance in the human body. This lack of an attack response can be important to maintaining health, for example, when the immune system leaves the body's own cells and proteins alone and only targets foreign substances that do not belong. Immune tolerance is also vital for healthy pregnancies and successful organ transplants and can occur naturally or be induced. Malfunctions of the immune system can lead it to attack substances that it shouldn't, such as the body's own cells. This lack of tolerance is referred to as an autoimmune disorder, and treatments for most of the related diseases are still being developed.
The primary function of the immune system is to fight off invading foreign substances, including viruses and bacteria, that are potentially harmful to the individual's health. It does this by developing antibodies which are specifically designed substances that attack foreign material that invades the body. There are many substances in the body that need to be there, however, and don't require an attack response from the immune system. Immune tolerance is the term for this lack of response, and its presence is vital for health. It is crucial for the immune system to be able to properly determine when a response is necessary or when tolerance is required.
There are many instances in which immune tolerance is vital to maintaining health. It is important for the immune system to avoid attacking the body's own cells and proteins, as well as other substances, such as hormones, enzymes, and even dental fillings. Another time when immune tolerance is extremely important is when a woman is pregnant so that the immune system does not attack the developing fetus, which is actually considered foreign material by the mother's body. During pregnancy, hormones suppress the immune response so that the unborn baby is tolerated.
It is also possible to induce immune tolerance with medication. This is done when a patient has an organ transplant. The new organ, a foreign substance to the patient's body, can be attacked by the immune system with life threatening consequences. Medications suppress the immune response and teach the body to accept the new organ as its own. In some cases, these medications are taken for a specific amount of time, but treatment is frequently required for the rest of the patient's life.
In certain disorders, immune tolerance fails and the system turns on the body's own cells. These conditions are autoimmune disorders and examples include lupus, psoriasis, rheumatoid arthritis, and AIDS. When these disorders are present, the immune system attacks part of the body, thereby causing pain, inflammation, and a variety of other symptoms. There currently are no cures for autoimmune disorders; there are treatments available for the symptoms, however, and new ones being developed. The hope is that someday treatments will be available that teach the immune system to tolerate the cells being attacked.
