Types of Autoimmune Diseases, Causes & Blood Tests

Autoimmune disorders are those diseases that occur as a result of the body’s immune system attacking different cells, tissues, organs or the entire body. The body has a number of mechanisms to prevent the immune system from attacking its own tissues but under certain conditions, these self regulating mechanisms may fail, leading to an autoimmune disease.

Causes of Autoimmune Diseases

When a foreign substance or microorganism enters the body, the proteins (antigens) are detected by the immune system and antibodies are produced against these antigen. Antibodies enable the immune cells to identify foreign invaders like viruses and bacteria, and initiate an appropriate response to neutralize these pathogens. In an autoimmune disorder, the immune system produces antibodies against the body’s own tissues and this causes the immune cells to attack the specific tissue or organ. The body has a suppressing mechanism to prevent this from occurring, known as the the T-suppressor cell system, but this may fail.

Possible causes of autoimmune diseases include :

  • Genetic factors.
  • Infection. Certain bacteria or viruses may affect the T-suppressor cell system or trigger antibodies that target the body’s own tissues which may appear similar to the pathogen. Alternatively certain infections may trigger a change in the body’s own molecules thereby rendering it ‘foreign’ to the immune system.
  • Drugs. Certain medication may affect the T-suppressor cells.
  • Sequestrated antigens. Certain cells and compounds present in the body are isolated from the body’s immune system, like sperm. In the event that these cells or compounds trigger the immune system, autoantibodies may be formed.
  • Organ rejection after transplants are not an autoimmune disease but may have an effect similar to sequestrated antigens and trigger a reaction against other tissues.

Types of Autoimmune Diseases

Broadly, autoimmune diseases can be divided into two categories :

  1. Organ specific autoimmune diseases where the immune system targets specific cells, tissues or organs.
  2. Generalized autoimmune diseases where the immune system may attack the body’s organs or tissues without discriminating among different types or target cells that are common to most organs, like connective tissue.

Examples of Organ Specific Autoimmune Diseases

Examples of Generalized Autoimmune Diseases

  • Systemic lupus erythematosus (SLE)
  • Rheumatoid arthritis (RA)
  • Scleroderma
  • Sarcoidosis
  • Guillain-Barre Syndrome

Blood Tests for Autoimmune Diseases

Tests for organ specific autoimmune disorders may have to focus on specific antibodies like testing for thyroid antibodies in Hashimoto’s thyroiditis. One of the most common blood tests for detecting autoimmune disorders is ANA (antinucelar antibodies), also known as ANF (antinuclear factor) while other tests like C-reactive protein (CRP) may also be useful for detecting autoimmune diseases. An ESR (erythrocyte sedimentation rate) may be conducted to evaluate inflammation not related to an infection or other causes. Certain genetic autoimmune diseases may be detected by testing for the HLA-B27 antigen and a positive test may indicate a higher risk for developing these disorders if there is a family history of the specific autoimmune disease.

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