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Sometimes the immune systems do not work in a normal way. The body, unfortunately, produces antibodies or sensitized T-cells against its own tissues.
It results in the destruction of cells or change in their function. The immunity developed against their, own structure is known as autoimmunity.
Causes:
Though the exact cause is not known, yet drugs, chemicals, genetic mutations etc. may cause.
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Autoimmune diseases:
The autoimmune diseases depend on the type of ‘self-antigen’, involved. For example ‘self-antigen’ for RBC causes destruction of its own RBC resulting in chronic anemia. If the ‘self-antigen’ is a muscle cell, then it results in the destruction of its own muscles resulting in a disease called myasthenia gravis; if the self antigens are liver cells, then it develops chronic hepatitis due to destruction of its own hepatic cells. These are the examples of some degenerative diseases.
Possible Treatment:
(a) Plasmapheresis:
The reactive autoantibodies are removed from the plasma and are again transfused into the patient.
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(b) T-cell vaccination:
Vaccination by using T-cells can be a successful treatment.
(c) Application of Immunosuppressant’s:
Some immunosuppressive drugs (Ex. Cartico steroids, cyclophosphamide and azathioprine etc.) reduce the severity of autoimmune diseases. But it increases the risk of cancer and other diseases as it suppresses the overall immune system.
(d) Use of Stem cells:
It is modern technique in which adult haemopoitic stem cell transplantation is done.
(e) Use of Monoclonal Antibodies:
The monoclonal antibodies have been used successfully to treat autoimmune diseases.
Immunodeficiency:
Sometimes people are born without B-cells and T-cells in their body. This deficiency makes them highly susceptible to diseases. The most serious type of disorder is a congenital disease known as Severe Combined Immunodeficiency (SCID), in which both B-cells and T-cells are absent. These patients become highly susceptible even to minor infections. In developed countries such babies are tried to be kept alive in germ free “isolation suits”.
Immune System Disorders:
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Allergies:
It is the hypersensitiveness of a person to some foreign substances, coming in contact with or entering the body.
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Allergens:
The substances that cause allergic reactions are called allergens. These are generally weak antigens. These include pollen grains, dust, chemicals, drugs, fabrics, plant, cold, heat, sunlight, some food stuffs, animals, bacteria etc.
Cause:
Any person can become allergic to anything at any time. Some people also have ‘allergic’ tendency. Their allergies are called atopic allergies, because they are caused by a non-ordinary response of the immune system. The allergic reactions are hereditary and are passed to the next generation. It is characterised by the presence of large quantity of reagins or sensitizing antibodies or IgE antibodies in the blood.
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The allergen and several IgE antibodies get attached to the mast cells and basophils which burst releasing histamine. More histamines are released during allergic reactions. Usually allergic reactions are very rapid. The histamines cause inflammatory responses.
Symptoms:
The common symptoms of allergic reactions are inflammation of mucous membrane, skin rashes, frequent sneezing, watering of eyes and even inability to breathe. In asthma, the lower portions of the respiratory system are severely affected. In eczema, the skin becomes red with minute blisters and can affect any part of the body.
Some forms of allergy:
(i) Hay fever:
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The histamine causes local intranasal vascular dilation. The symptoms of this allergic form are swollen, reddened and watering eyes and running nose etc.
(ii) Asthma:
In “allergic” type of persons, the allergen-reagin reaction occurs in the bronchioles of the lungs. The mast cells release the slow-reacting substances of anaphylaxis which causes spasm of bronchiolar smooth muscles. It causes difficulty in breathing.
(iii) Anaphylactic shock:
It involves all the tissues of the body, rather than the blood. The allergen, such as a dose of pencillin or a single bee sting cause rupturing of mast cells and release of histamine. This histamine causes dilation of arteries, so that large amount of fluid passes from the blood to the tissues. It results in drastic fall of the blood pressure. The patient may become unconscious or may die in a short time.
Treatments:
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In most cases antihistamine decreases the effect of histamine, except in case of asthma.
