IMMUNE SUSTEM
Immunology is the study of body’s defense from infectious agents and other foreign substances in the environment. This defense includes a mechanical barrier (the skin), protective chemical substances in the blood and tissue fluids, and physiologic reactions to injury or infection.
The immune system has three major properties:
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to recognize and distinguish a vast number of different molecules;
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to respond vigorously against foreign substances;
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to provide immunity from a disease.
The body’s ability to protect itself from a disease is called immunity. It may be natural or acquired. Natural immunity is genetically determined. Acquired immunity is active or passive. Passive immunity is only temporary. Active immunity is permanent and results from previously suffered disease or vaccination.
Immunogens or antigens are substances stimulating an immune response. Antibody is a substance produced in response to an infection. It combines with antigen and neutralizes it.
Complements, phagocytes, WBCs and others help to protect the body against a disease and infection.
Immune response is usually carried by body’s lymphatic system. It is a network of thin-walled vessels which drain lymph from between the body cells into the blood stream. Rounded small bean-shaped structures called lymph nodes form part of the lymphatic system. They have 3 main functions:
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to filter out and destroy foreign substances such as bacteria and dust;
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to produce some of WBCs;
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to produce antibodies.
Specialized lympoid tissue, similar to lymph nodes , includes tonsils, adenoids, appendix and spleen.