Encyclopedia of Life Sciences - Vol. 2

By Anne O’Daly | Go to book overview

AUTOIMMUNE DISORDERS

Autoimmune disorders are a group of diseases in which the immune system attacks the body’s own tissues

In healthy people the immune system fights disease because it is able to distinguish between self, the body’s own tissues, and nonself, foreign organisms and substances such as viruses, bacteria, and toxins that have entered the body (see BACTERIA; IMMUNE SYSTEMS; VIRUSES). In people with autoimmune disorders, the immune system malfunctions and produces abnormal antibodies (see ANTIBODIES) called autoantibodies. These antibodies attack and destroy the body’s own tissues.

Autoimmune disorders range from minor diseases that cause a skin rash to serious ones that can be fatal. At present doctors recognize up to about 80 diseases as having an autoimmune cause, and this number is likely to increase as more diseases oí previously unknown cause are found to be autoimmune. Autoimmunity can affect any organ or tissue in the body, causing inflammation and usually permanent damage.

Well-known autoimmune disorders include type I (insulin-dependent) diabetes mellitus (see DIABETES), multiple sclerosis (see box on page 165), rheumatoid arthritis (see ARTHRITIS), and systemic lupus erythematosus (SLE). Autoimmune disorders are uncommon in children but common in women: about 75 percent of sufferers are women. It is estimated about 50 million people (about 20 percent of the population) in the United States have an autoimmune disorder. People with such a disorder are at increased risk of developing other autoimmune disorders, although none of them is contagious.


Causes

The cause of the abnormal immune reactions in autoimmune disorders is not known precisely. The disorders tend to run in families, a fact that suggests genes and inheritance play a part (see GENETIC DISEASES). No single gene is known to cause an autoimmune disorder; it is believed that the risk of developing an autoimmune disorder is determined by several genes, some of which are necessary for a specific disorder, while others predispose an individual to general autoimmunity. In many cases different members of the same family have different autoimmune disorders.


CORE FACTS
In autoimmune disorders the immune system attacks
and destroys the body’s own tissues,
Doctors think there are currently over 80 diseases
that have an autoimmune cause. They include
multiple sclerosis, rheumatoid arthritis, and type 1
diabetes mellitus.
The underlying causes of autoimmune disorders are not
fully understood, but involves genes and environmental
triggers, such as viruses and bacteria,
Autoimmune disorders are generally long term and
without a cure, although symptoms can be controlled
with corticosteroid, immunosuppressant, and
nonsteroidal anti-inflammatory drugs.

The hand of someone
suffering from scleroderma.
As the disease changes the
skin, it becomes shiny,
tight, and thickened, and
the fingers become even
harder to bend
.

Some viral and bacterial infections can trigger autoimmunity in people who are already genetically susceptible. For example, rheumatic fever is an autoimmune disorder that develops after a streptococcal infection, usually of the throat. Antigens are substances that provide an immune response. Medical researchers believe that the antibodies produced by the immune system against antigens of the streptococcal bacteria cross-react with structurally similar molecules in heart tissue. This reaction causes inflammation of the heart valves and may lead to permanent damage and scarring of the valves.

Certain drugs have been shown to trigger autoimmune disorders. For example, hemolytic anemia, in which there is excessive destruction of red blood cells, sometimes develops after treatment with the antibiotic penicillin, with methyldopa (a drug that lowers blood pressure), or with the antimalarial drug quinine (see ANEMIA).

Recent research suggests that autoimmune disorders may result from the transfer of fetal and maternal cells during pregnancy or childbirth. Fetal cells can linger in maternal blood decades after childbirth. Researchers found higher numbers of fetal cells in the blood of women with scleroderma than in that of women who did not have the condition. Scleroderma is an autoimmune disorder in which there is degeneration of the skin, lungs, and internal organs. It is thought that these circulating foreign fetal cells trigger the disease and may also be responsible for other autoimmune disorders. This theory may also explain why autoimmune immune disorders are more common in women.


CONNECTIONS
IMMUNE SYSTEMS protect against disease. In many animals ANTIBODIES help the body recognize and protect against invaders, such as microorganisms.
MULTIPLE SCLEROSIS. ARTHRITIS, ANEMIA, and certain types of DIABETES are autoimmune disorders.

-164-

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Encyclopedia of Life Sciences - Vol. 2
Table of contents

Table of contents

  • Title Page i
  • Contents iii
  • Useful Information 148
  • Artificial Life 149
  • Asthma 153
  • Atmosphere 154
  • Atp Production 158
  • Autism 161
  • Autoimmune Disorders 164
  • Bacteria 167
  • Bats 173
  • Beetles 177
  • Biennial Plants 179
  • Biochemistry 180
  • Biodiversity 183
  • Bioethics 187
  • Biogeography 192
  • Biological Control 195
  • Biological Warfare 197
  • Biology, History and Philosophy of 200
  • Bioluminescene 205
  • Biomes and Habitats 208
  • Bionics 212
  • Biorhythms 216
  • Biosphere 220
  • Biotechnology 221
  • Birds 228
  • Birds of Prey 234
  • Blood 238
  • Bone 248
  • Botanical Gardens 251
  • Botany 253
  • Brain 255
  • Bulbs and Corms 265
  • Butterflies and Moths 267
  • Cacti and Succulents 272
  • Caecilians 275
  • Calcium 277
  • Calorie 279
  • Camouflage and Mimicry 281
  • Index 287
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