8.2.5 ALLERGIES AND 8.2.6 AUTO IMMUNITY

8.2.5 Allergies 
  • When you have gone to a new place and suddenly you started sneezing, wheezing for no explained reason, and when you went away, your symptoms dissappeared. 
  • Did this happen to you? Some of us are sensitive to some particles in the environment. 
  • The above-mentioned reaction could be because of allergy to pollen, mites, etc., which are different in different places. 
  • The exaggerated response of the immune system to certain antigens present in the environment is called allergy. 
  • The substances to which such an immune response is produced are called allergens. 
  • The antibodies produced to these are of IgE type. 
  • Common examples of allergens are mites in dust, pollens, animal dander, etc. 
  • Symptoms of allergic reactions include sneezing, watery eyes, running nose and difficulty in breathing. 
  • Allergy is due to the release of chemicals like histamine and serotonin from the mast cells. 
  • For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions studied. 
  • The use of drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy. 
  • Somehow, modern-day life style has resulted in lowering of immunity and more sensitivity to allergens – more and more children in metro cities of India suffer from allergies and asthma due to sensitivity to the environment. 
  • This could be because of the protected environment provided early in life. 

8.2.6 Auto Immunity

  • Auto Immunity Memory-based acquired immunity evolved in higher vertebrates based on the ability to differentiate foreign organisms (e.g., pathogens) from self-cells. 
  • While we still do not understand the basis of this, two corollaries of this ability have to be understood. 
  • One, higher vertebrates can distinguish foreign molecules as well as foreign organisms. 
  • Most of the experimental immunology deals with this aspect. 
  • Two, sometimes, due to genetic and other unknown reasons, the body attacks self-cells. 
  • This results in damage to the body and is called auto-immune disease. 
  • Rheumatoid arthritis which affects many people in our society is an auto-immune disease.

Other Auto-immune Disorders-
  • Myasthenia gravis: Antibodies bind to nerves and make them unable to stimulate muscles properly.
  • Rheumatoid arthritis: The immune system produces antibodies that attach to the linings of joints. Immune system cells then attack the joints, causing inflammation.
  • Systemic lupus erythematosus (lupus): People with lupus develop autoimmune antibodies that can attach to tissues throughout the body. The joints, lungs, blood cells, lungs, and kidneys are commonly affected.
  • Inflammatory bowel disease (IBD): People with lupus develop autoimmune antibodies that can attach to tissues throughout the body. The joints, lungs, blood cells, nerves, and kidneys are commonly affected
  • Multiple sclerosis (MS): The immune system attacks nerve cells, causing symptoms that can include pain, blindness, weakness, poor coordination, and muscle spasms
  • Type 1 diabetes mellitus: Immune system antibodies attack and destroy insulin-producing cells in the pancreas.
  • Guillain-Barre syndrome: The immune system attacks the nerves controlling muscles in the legs and sometimes the arms and upper body. Weakness results, which can sometimes be severe.
  • Chronic inflammatory demyelinating polyneuropathy: Similar to Guillian-Barre, the immune system also attacks the nerves in CIDP, but symptoms last much longer.
  • Psoriasis: In psoriasis, overactive immune system blood cells called T-cells collect in the skin. The immune system activity stimulates skin cells to reproduce rapidly, producing silvery, scaly plaques on the skin.
  • Graves' disease: The immune system produces antibodies that stimulate the thyroid gland to release excess amounts of thyroid hormone into the blood (hyperthyroidism). Symptoms of Graves' disease can include bulging eyes as well as weight loss, nervousness, irritability, rapid heart rate, weakness, and brittle hair.
  • Hashimoto' thyroiditis: Antibodies produced by the immune system attack the thyroid gland, slowly destroying the cells that produce thyroid hormone. Low levels of thyroid hormone develop (hypothyroidism), usually over months to years. Symptoms include fatigue, constipation, weight gain, depression, dry skin, and sensitivity to cold.
  • Vasculitis: The immune system attacks and damages blood vessels in this group of autoimmune diseases. Vasculitis can affect any organ, so symptoms vary widely and can occur almost anywhere in the body.

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