THE IMMUNE SYSTEM AND ITS LINK TO RHEUMATIC DISEASES |
Our immune system is an amazing network of cells that function from very
basic to highly complex levels. The purpose of this entire system is to
protect us from infection and monitor our own cells for any early
damage. Sometimes, however, the system goes awry and misreads signals.
Because our own cells are rarely perceived by our own immune system to
be threatening, this results in an “attack” on our body's own cells. This
leads to illnesses called autoimmune (self-immune) diseases such as rheumatoid
arthritis, systemic lupus
erythematosus, and vasculitis.
Fast Facts
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When our immune system gets confused, it can lead to
unanticipated damage to our own bodies.
Genetic background as well as particular environmental
exposures creates a situation where that individual patient may have
an increased risk for developing an autoimmune illness.
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New biologic therapies offer specific “bullets” to
target as finely as possible the components of our immune system.
What Autoimmunity Is
There are at least four components of the immune system. They can be differentiated into innate and acquired systems with humeral and cellular components. The innate system is an “ancient” system that recognizes foreign invaders such as bacteria and requires mostly cell to cell interactions without invoking antibodies. The more recently “evolved” adaptive immune system is much more intricate in its complexity, and changes as we go through our life span. Together these processes dictate where and to what extent the immune system exerts its influence.
The immune system is a symphony that ranges from basic notes (innate immunity)
to a highly complex orchestra of cells demonstrating an extensive ability to
communicate with one another. The complexity of this system and its ability
to protect us is astounding. It 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) while, all the time, differentiating
our normal cells from intrinsic abnormalities and extrinsic invasion.
However, when the clinical balance is somehow disturbed, our own immune system
actually gets confused, causing damage to our own joints, muscles, blood vessels
and kidneys.
What Causes the Change
Why this happens is not entirely clear, but there are potential reasons.
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 and,
together, the antibodies and the viral components to which they bind deposit
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.
There are also genetic factors which influence our immune response as is clearly the case with rheumatoid
arthritis. Patients who have been shown to have a genetic marker called HLA – DR4 have an increased risk of developing rheumatoid arthritis.
However, more sophisticated studies have shown that this is only part of the
story and that other immunologic and genetic variables control the disease
response. In patients who have this genetic component, environmental stimuli
(such as viruses or even smoking) cause the immune system to react in a way
that is activated. In a genetically predisposed patient, this immune response
triggers rheumatoid arthritis by aggregating cells within the lining of the
joint and elsewhere.
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.
How Autoimmune Diseases are Diagnosed
These diseases are 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 involved system may be required. If treatment is required, the drugs used may include corticosteroids, and often other drugs such as methotrexate which may effect the immune system. Careful monitoring of side effects is imperative, and only a physician experienced with these drugs and diseases should monitor the therapies.
Your physician will review a combination of your 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.
How Autoimmune Diseases are Treated
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 therapies, called the biologic
therapies, are directed against the small molecules which orchestrate our own immune response. These drugs include inhibitors of tumor necrosis factor (TNF), IL1, as well as others. Therefore, with specific targeted therapy against specific messengers, we can change our immune response, both for the good and 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.
Points to Remember
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Diseases may be difficult to diagnose, and treatment choices are very
complicated. A rheumatologist is specifically trained to diagnose and
treat these illnesses.
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Patients treated with new biologic therapies must be carefully monitored
for adverse events to help achieve a positive outcome.
To find a rheumatologist
For a listing of rheumatologists in your area, click
here.
Learn more about rheumatologists and rheumatology
health professionals.
For more information
The American College of Rheumatology has compiled this list to give you
a starting point for your own additional research. The ACR does not endorse
or maintain these Web sites, and is not responsible for any information
or claims provided on them. It is always best to talk with your rheumatologist
for more information and before making any decisions about your care.
Arthritis Foundation
www.arthritis.org
American Autoimmune
Related Diseases Association
http://www.aarda.org/
Written May 2005
Written by Jonathan Scott Coblyn, MD, and reviewed by the American College
of Rheumatology.
