Autoimmunity generally leads to the destruction of one’s own tissues causing diseases. Autoimmune diseases are defined as a group of disorders in which tissue injury is caused by humeral or cell mediated immune response to self antigens. However, autoimmunity literally means protection against self, but normally autoimmunity produces tissue injury and tissue damage in one’s own body. Hence the term autoimmunity is a misnomer. The term auto allergy has been suggested as an alternative. However the term autoimmunity is widely used.
Autoimmunity was first observed by Metalnikoff in 1990 in guinea pigs. He injected guinea pigs with their own spermatozoa. The guinea pigs produced sperm immobilising antibodies. Autoimmune disease was first observed by Donath and Landsteiner in 1904. They identified circulating auto antibodies in paroxysmal cold haemoglobinuria, a haemolysin which binds with the patient’s erythrocytes at low temperature and produces complement dependent haemolysis on warming.
Characteristics of autoimmune diseases
•Autoimmune diseases are caused by autoimmune response.
• The auto antigen which produces autoimmune disease is one individual, will cause the same disease in an experimental animal when the same antigen is injected.
• The disease can be passively transferred by the transfer of auto antibodies or sensitised lymphocytes.
• In autoimmune disease an elevated amount of immunoglobulin is produced.
• Immunoglobulins or their products are deposited at the sites of election such as renal glomeruli.
• Lymphocytes and plasma cells accumulate at the sites of lesions.
CAUSES OF AUTOIMMUNE DISEASES
These are caused by the following factors:
1. Sequestered antigens
3. Cross- reacting antigens
4. Cessation of tolerance
5. Loss of immunoregulation.
Pathogenesis of autoimmune diseases
In autoimmune diseases one’s own tissues are damaged. The tissue damage is caused by the activity of antibodies, cytotoxic or lymphocyte producing T-cells, K-cells and complement.
The tissue damage that occurs in autoimmune disease is mediated by one or more of the type 2 or type 5 hypersensitivity reactions.
Classification of Autoimmune diseases
These Diseases are broadly classified into 3 groups. They are,
• Haemolytic Autoimmune diseases
• Localised Autoimmune diseases
• Systemic Autoimmune diseases.
List of Autoimmune diseases
The following are the commonly found autoimmune diseases.
1. Autoimmune haemolytic anaemia
4. Addison’s disease
5. Myasthenia gravis
6. Lupus erythematosus
7. Rheumatoid arthritis
8. Hashimoto’s disease
Diagnosis of autoimmune diseases
These diseases are diagnosed by clinical symptoms. However, the clinical symptoms are confirmed by detecting the auto antibodies in the serum of the patients, the auto antibodies are demonstrated by immunoflurescent antibody test, haemagglutination, antiglobulin reaction, complement fixation, immunodiffusion, radioimmunoassay, etc.
Treatment of autoimmune diseases
• Thyrotoxicosis can be treated with antithyroid drugs.
• Haemolytic anaemia can be treated with vitamin b-12.
• Myasthenia gravis can be treated with choline esterase inhibitors.
• Rheumatoid arthritis can be treated with anti-inflammatory drugs.
• Lupus erythematosus can be treated with immunosuppressive or antibiotic drugs such as corticosteroid, cyclophosphamide and azothioprine.
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