SPECIFIC DEFENSES OF THE HOST - antigens might be bacteria...

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SPECIFIC DEFENSES OF THE HOST: THE IMMUNE  RESPONSE     In addition to nonspecific resistance, another way we defend against invaders is innate resistance —this is resistance that is “built in,” such as human resistance to many animal diseases. Also,  susceptibility to human diseases can vary from one person to another. A person’s resistance can  vary due to: Genetic factors \Gender Age Nutritional status General health   This chapter concentrates on another important means of defense—the immune response.      IMMUNITY   This is a specific response to invasion by a particular foreign organism or other foreign  substance. The immune system recognizes these as foreign----not belonging in the body---and  develops an immune response against them. Anything that provokes an immune response is  called an antigen. The immune response involves the production of antibodies and specialized 
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lymphocytes that work to destroy or inactivate that particular antigen. Organisms that act as 
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Unformatted text preview: antigens might be bacteria, viruses, protozoa, fungi or helminths. Substances include pollen, insect venom, and transplanted tissue. Body cells that change and become cancerous may also be perceived as foreign and act as antigens, so cancers may be eliminated in very early stages by our immune system. HUMORAL (ANTIBODY-MEDIATED) IMMUNITY This involves the production of antibodies, which are found in extracellular fluids such as blood plasma, lymph, and mucus secretions. Antibodies are produced by B lymphocytes (B cells) which have changed in response to the presence of foreign material and become plasma cells. This type of defense works best against: • Most bacteria • Bacterial toxins • Viruses that have not yet invaded cells • Part of the response against transplanted tissue...
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SPECIFIC DEFENSES OF THE HOST - antigens might be bacteria...

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