Immune System
The immune system is a collection of special cells and chemicals that fight infection-causing agents such as bacteria and viruses. An autoimmune disorder occurs when a person's immune system mistakenly attacks their own body tissues.
Normally the immune system's army of white blood cells helps protect the body from harmful substances, called antigens. Examples of antigens include bacteria, viruses, toxins, cancer cells, and blood or tissues from another person or species. The immune system produces antibodies that destroy these harmful substances.
But in patients with an autoimmune disorder, the immune system can't tell the difference between healthy body tissue and antigens. The result is an immune response that destroys normal body tissues.
What causes this to happen is not exactly known. It is now commonly thought that there is a genetic predisposition to developing an autoimmune disorder, and this type of difficulty seems to run in families. However, family members can be affected by different disorders; for example, one person may have diabetes, while another has rheumatoid arthritis. It seems that genetic susceptibility alone is not enough to trigger an autoimmune reaction, and other factors must contribute. Additionally, in about three-quarters of cases the persons who are affected are women. The onset of these disorders has also been associated with infections - some disorders seem to be triggered or worsened by particular infections.
Autoimmune disorders can affect nearly every organ and system of the body. Some autoimmune disorders include:
- Diabetes (Type I) - affects the pancreas. Symptoms include thirst, frequent urination, weight loss and an increased susceptibility to infection.
- Graves' disease - affects the thyroid gland. Symptoms include weight loss, elevated heart rate, anxiety and diarrhoea.
- Multiple sclerosis - affects the nervous system. Depending on which part of the nervous system is affected, symptoms can include numbness, paralysis and vision impairment.
- Psoriasis - affects the skin. Features include the development of thick, reddened skin scales.
Rheumatoid arthritis - affects the joints. Symptoms include swollen and deformed joints. The eyes, lungs and heart may also be targeted.
- Systemic lupus erythematosus - affects connective tissue and can strike any organ system of the body. Symptoms include joint inflammation, fever, weight loss and a characteristic facial rash.