Active immunity:
- When the host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body.
- Active immunity is slow and takes time to give its full effective response.
- Injecting microbes deliberately during immunization or infection of microbes naturally induce active immunity.
Passive immunity:
- Ready made antibodies are directly given to protect the body against foreign agents.
- Colostrums of mother contain abundant antibody (IgA) to protect the child.
- Foetus receives some antibody (IgG) from mother during pregnancy.
Vaccination and Immunization:
- The principle of immunization or vaccination is based on the property of ‘memory, of the immune system.
- In vaccination, a preparation of antigenic protein of pathogen or inactivated/weakened pathogen (vaccine) is introduced into the body.
- The antibodies produced in the body against vaccine, (antigen) would neutralize the pathogenic agents during actual infection.
- The vaccines also generate memory B and T-cells that recognize the pathogen quickly on subsequent exposure.
Passive immunization:
- Preformed antibody or antitoxin injection for specific antigen.
- Injection of antivenin for snake bite to counter the snake venom
Vaccine production:
- Recombinant DNA technology has allowed the production of antigenic polypeptide of pathogen in bacteria and yeast.
- Vaccine produced by this approach allows large scale production of antigen for immunization. E.g. hepatitis-B produced from yeast.
Allergies:
- The exaggerated response of the immune system to certain antigens present in the environment is called allergy.
- The substance to which such immune response is produced is allergen.
- IgE is produced during allergic reactions.
- Common allergens are dust, pollen, animal dander etc.
- Common symptoms are sneezing, watery eyes, running nose etc.
- Allergy is due to release of histamine and serotonin from the mast cells.
- Drugs like anti-histamine, adrenalin and steroid quickly reduce symptoms of allergy.
Auto immunity:
- Memory based acquired immunity able to distinguish foreign molecules or cells (pathogen) from self-cells.
- Sometimes due to genetic and other unknown reasons the body attacks self cells. This results in damage to the body cells and is called auto-immune disease. E.g. Rheumatoid arthritis, Multiple sclerosis.
Immune system in our body:
- The immune system consists of
- Lymphoid organs
- Lymphoid tissues
- T and B-cells.
- Antibodies.
- Immune system recognizes the foreign antigens, responds to them and remembers them.
- The immune system also plays important role in:
- Allergic reaction
- Auto immuno diseases and
- Organ transplantation.
- Primary lymphoid organs: bone marrow and thymus, production and maturation of lymphocytes take place.
- Secondary lymphoid organs: spleen, tonsil, lymph node, Payer’s patches of small intestine and appendix, where proliferation and differentiation of lymphocyte take place.
- Bone marrow is the main lymphoid organ where all blood cell including lymphocytes are produced.
- Thymus is a bilobed organ located near the heart, beneath the breastbone.
- B-lymphocytes are produced and matured in bone marrow.
- T-lymphocytes are produced in bone marrow but matured in thymus.
- The spleen
- Large bean shaped organ mainly contain lymphocytes and phagocytes.
- Acts as a filter of the blood by trapping blood-borne micro-organisms.
- Spleen is also serves as the large reservoir of erythrocytes.
- Lymph node:
- Small solid structure located at different points along the lymphatic system.
- Traps the micro-organisms or other foreign antigens.
- Antigen trapped into the lymph node responsible for activation and differentiation of lymphocytes and cause immune response.
- Mucosal associated lymphoid tissues (MALT):
- Located within the lining of major tract (respiratory, digestive and urinogenital tracts)
- It constitutes 50% of lymphoid tissues.
AIDS:
- Stands for Acquired Immuno Deficiency Syndrome.
- Deficiency of immune system that acquired during life time and not congenital disease.
- Syndrome means a group of symptoms.
- AIDS was first reported in 1981.
- AIDS is caused by HIV (Human Immuno deficiency Virus)
- HIV is retrovirus, having RNA as the genetic material.
Method of transmission:
- Sexual contact with infected persons.
- Transfusion of contaminated blood and blood products.
- Sharing infected needles as intravenous drug user.
- From infected mother to the foetus through placenta.
CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : harekrushnagiri@yahoo.com
