classnotes7 - Immune system. One of the more complex...

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Immune system. One of the more complex systems we’re looking at. An immune response (a response to a pathogen) can be of two types: (pathogen - disease causing organism) 1) Non specific. Anything foreign is attacked. 2) Specific. The immune system attacks only one kind of pathogen. I. Non-specific defenses (could be labeled innate defenses): - skin: acts as a barrier, also secretes acids that inhibit bacteria. - body fluids: sweat, saliva, tears, all contain anti-microbial enzymes - stomach acid: kills many bacteria - mucous membranes in nose and trachea trap many pathogens. If something does get through, the first line of defense is generally an inflammatory response [Fig. 24.2, p. 487] : tissue damage --> histamine is released by damaged cells --> dilates blood vessels --> blood flow to the damaged area increases --> increasing number of phagocytes show up. Phagocytes engulf (“eat”) bacteria and damaged cells. They disinfect the area. In the process, they often die and contribute to the pus found in inflamed areas. This inflammatory response can be more widespread: - bacteria in blood stream can cause overall increases in phagocytes. - fever can sometimes slow bacterial growth, though if too high this is dangerous. - immune system can be overwhelmed and respond massively, generating septic shock (a common cause of death in hospitals). Other nonspecific responses include: - release of interferon (inhibits viral replication)
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- a cell infected with a virus makes interferon. This triggers proteins in other cells that slow viral replication [Fig. 24.1B p. 486] . - complement proteins - interact with microbes or the immune system. - mark surfaces of microbes so that phagocytes can get them easier. - sometimes cut holes in microbial membranes, killing or weakening the microbes . Lymphatic system [Fig. 24.3, p. 488] - in addition to moving interstitial fluid back to the heart (& circulatory system), the lymphatic system also helps remove pathogens. - lymph nodes are packed with lymphocytes & phagocytes - these can filter the fluid, attack bacteria & viruses. - attack can be specific or non-specific. - efficient system since much fluid in the body is filtered this way. II. Specific defenses (acquired immunity) Some definitions: antigen - a molecule (usually on the surface of a bacterium or virus) that causes an immune response. An antigen may have several different “antigenic determinants”.
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This note was uploaded on 07/21/2011 for the course BIO 101 taught by Professor Staff during the Spring '08 term at Northern Virginia Community College.

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classnotes7 - Immune system. One of the more complex...

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