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Our immune system is an amazing network of cells that function from very basic to highly complex levels. The purpose of this system is to protect us from our environment and watch for any early damage in our own cells. Sometimes, however, the system goes awry and misreads signals. As a result, our defenses do not recognize our own body at work, and begin “attacking” cells. This leads to illnesses called autoimmune (self-immune) diseases such as
rheumatoid arthritis (inflammation of the joints),
systemic lupus erythematosus (commonly known as “lupus,” an inflammatory disease of connective tissue), and
vasculitis (inflammation of a vessel of the body).
The immune system allows us to identify and destroy foreign invaders (bacteria, viruses, fungi, etc) and survey our own cells to prevent them from growing uncontrollably (cancer and other disorders). Its complexity and ability to protect us is astounding.
The immune system can be divided into two components: the innate (born with) immune system and adaptive (develop through life) immune system. The innate component is the first line of defense. It reacts very quickly to fight off "foreigners" such as viruses and bacteria and identifying damaged cells. Evolutionarily it has been present for thousands of years. Cells of the innate immune system try to destroy the foreign intruders by attacking them and releasing toxic molecules. It also releases other signals to recruit more inflammatory cells to join the fight.
The adaptive component is slower to react taking several days to activate T cells, B cells and make antibodies to fight off foreign invaders. It develops as we age and is built up by vaccines. The adaptive immune system also produces antibodies that remember the foreign invader so that it can recognize it quicker in the future.
There are times, however, when the immune system gets confused. It can no longer distinguish a "foreigner" from your own tissue. It mistakenly directs inflammation against your own tissue causing damage and disease. This damage can occur in your joints, muscles, blood vessels, kidneys, virtually any tissue in your body. Illnesses from this type of damage are called autoimmune (self- immune) diseases. They include rheumatoid arthritis, systemic lupus, and vasculitis to name a few.
Why this happens is not entirely clear. In some of these illnesses, the blood vessels are innocent bystanders. As our bodies are fighting a virus (e.g., Hepatitis C), we form antibodies. Together, the antibodies and antigens collect in the blood vessels creating inflammation. This causes inflammatory disease, the extent of which is dependent upon where and how many blood vessels are involved.
Patients with a genetic marker called HLA-DR4 have an increased risk of developing rheumatoid arthritis. This is a blood test but it is not typically run as it can be nonspecific. Some patients have this genetic marker but never develop rheumatoid arthritis. We have learned through much research that genetics are only part of the story. Environmental stimuli (such as viruses and smoking) can also influence the immune system to react in a different ways causing disease instead of protecting your body. It typically takes both the right genetic background and environmental stimuli together leading your immune system towards a diseased state.
Similar processes occur in systemic lupus erythematosus. The genetic background, as well as particular environmental exposures, creates a situation where that individual patient has an increased risk for developing one of these illnesses.
Autoimmune diseases can be very difficult to diagnose, and the right treatment must be carefully chosen for the right disease at the right time. Each diagnosis requires a thorough history and physical exam, and often many laboratory tests. If the patient has vasculitis, a biopsy of the skin or other system of the body may be required.
If treatment is required, the drugs used may include corticosteroids such as cortisone as well as other drugs, such as methotrexate. These drugs suppress the immune system so careful monitoring of side effects is essential. Only a physician experienced with these drugs and diseases should monitor the therapies.
The physician will review a combination of medical history including that of any family members with autoimmune disease, a physical exam and the results of medical tests such as blood samples prior to making a diagnosis. This will probably include referral to a rheumatologist.
The key component of all of these diseases involves our own immune system, which contributes to the illness. So therapy targeting our own immune system can help alleviate the diseases themselves.
New biologic therapies are directed against the small molecules which orchestrate our own immune response. These drugs include tumor necrosis factor inhibitors (TNF), IL-6 inhibitors, inhibitors of T cell and B cell interaction and others.
By using specific targeted therapy against specific messengers, we can change our immune response, both for the good and for the bad. Any change in the immune system may control the disease, but may also subject us to different risks such as infection that need to be monitored by your rheumatologist.
Updated June 2015 by Jennifer Murphy, MD. Written by Erika Heidi Noss, MD, PhD and Jonathan Scott Coblyn, MD, and reviewed by the American College of Rheumatology Communications and Marketing Committee.
This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.
© 2015 American College of Rheumatology