Article
Aravind Kumar, Final BHMS
M.H.Medical College,
Muzaffarpur, Bihar.
Mob: 98354 42838
Email:doctor_aravind 02@yahoo.co.in
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The immune system can overreact, causing allergies
or autoimmune diseases. Likewise, a suppressed, absent, or destroyed immune
system can also result in disease and death.
Contagious Diseases
The most common Immunodeficiency is seen in infections as primary immuno deficiency and later as secondary immunodeficiency. Immunodeficiencies can affect B-lymphocytes, T lymphocytes, or phagocytes.
Allergy
Allergies result from immune system hypersensitivity to weak antigens that do not cause an immune response in most people. Allergens, the substances that cause allergies include dust, molds, pollen, cat dander, certain foods and some medicines such as penicillin.
After exposure to an allergen, some people make IgE antibodies as well as B and T memory cells. Subsequent exposure to the same allergen causes a massive secondary immune response that releases plenty of IgE antibodies. These bind to mast cells found usually in connective tissues surrounding blood vessels. Mast cells then release histamine, which starts the inflammatory response. Eczema is an itchy rash also caused by allergic reaction. In some individuals the histamine release causes life-threatening anaphylaxis or anaphylactic shock.
Autoimmune diseases:
The immune system usually distinguishes “self” from “nonself”. The immune system learns the difference between cells of the body and foreign invaders. Autoimmune diseases result when the immune system attacks and destroys cells and tissues of the body. Juvenile diabetes, Grave’s disease, Multiple sclerosis, Systemic lupus erythematosus and Rheumatoid arthritis are some of the autoimmune diseases.
Myasthenia gravis is due to muscle weakness caused by destruction of muscle-nerve connections. Antibodies attacking the myelin of nerve cells cause Multiple sclerosis. Systemic lupus erythematosus in a person is due to formation of a series of antibodies to their own tissues mainly kidneys, which is the leading cause of death in SLE patients and also the DNA in their own cellular nuclei. In Systemic Lupus Erythematosus (SLE), the immune system attacks connective tissues and major organs of the body. Rheumatoid Arthritis victims have damage to their joints. Some evidence supports Type I diabetes as an autoimmune disease. Juvenile diabetes results from the destruction of insulin-producing cells in the pancreas.
Immunodeficiency diseases
Immunodeficiency diseases result from the lack or failure of one or more parts of the immune system. Affected individuals are susceptible to diseases that normally would not bother most people. Genetic disorders, Hodgkin’s disease, cancer chemotherapy and radiation therapy can cause immunodeficiency diseases.
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Severe Combined Immunodeficiency (SCID) results from a complete absence of the cell-mediated and antibody-mediated immune responses. Affected individuals suffer from a series of seemingly minor infections and usually die at an early age. A small group suffering from adenosine deaminase (ADA) deficiency, a type of SCID is undergoing gene therapy to provide them with normal copies of the defective gene.
Acquired Immunodeficiency Syndrome (AIDS) is currently receiving most attention among the immunodeficiency diseases. AIDS is a collection of disorders resulting from the destruction of T cells by the Human Immunodeficiency Virus (HIV), a retrovirus. When HIV replicates in the human T cells, it buds from the T cell plasma membrane encased in a coat derived from the T cell plasma membrane. HIV selectively infects and kills T4 helper cells. The viral RNA is converted into DNA by the enzyme reverse transcriptase; this DNA can become incorporated into a human chromosome for months or years.
Cancer
Cells of the immune system, like those of other body systems can proliferate uncontrollably; the result is cancer. Leukemia’s are caused by the proliferation of white blood cells, or leukocytes. The uncontrolled growth of antibody-producing (plasma) cells can lead to multiple myeloma. Cancers of the lymphoid organs, known as lymphomas, include Hodgkin’s disease. Drugs and/or radiation can treat these disorders very successfully.
