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| Specific Defence Mechanism |
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| This mechanism provides protection against specific foreign materials and is often called the immune system. This system forms the third line of body's defence against microbes and harmful molecules. The most important characteristic of the immune system is that its cells have an ability to recognise body's own cells and macromolecules, from those which are foreign invaders or nonself. |
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| The foreign matter that enters the body and elicits a specific immune response by lymphocytes is an antigen (anti - antibody gen - generating) |
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| It stimulates the immune system to produce protective chemicals or special cells to destroy the antigens. These protective chemicals are called as antibodies. The protein molecules present on the surface of the foreign material act as antigens. Each antigen causes the formation of a specific antibody. Antibodies react with antigens and make them inactive or harmless. |
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