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 humoral 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 autoallergy has been suggested as an alternative. However, the term autoimmunity is widely used.
Autoimmunity was first observed by Metchnikoff in 1990 in guinea pigs. He injected guinea pigs with their own spermatozoa. The guinea pigs produced sperm immobilizing antibodies. Autoimmune disease was first observed by Donath and Landsteiner in 1904. They identified circulating autoantibodies in paroxysmal cold hemoglobinuria, a hemolysin which binds with the patient’s erythrocytes at low temperature and produces complement dependent hemolysis on warming.
Characteristics of Autoimmune Diseases
• Autoimmune diseases are caused by an autoimmune response.
• The autoantigen 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 autoantibodies or sensitized 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 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 hemolytic anemia
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 autoantibodies in the serum of the patients, the autoantibodies are demonstrated by immunofluorescent antibody test, haemagglutination, antiglobulin reaction, complement fixation, immunodiffusion, radioimmunoassay, etc.
Treatment of autoimmune diseases
• Thyrotoxicosis can be treated with antithyroid drugs.
• Haemolytic anemia 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 a corticosteroid, cyclophosphamide, and azathioprine.
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