Answers-Homework2_000SP08

Answers-Homework2_000SP08 - BILD 2 Homework #2 5/13/08 1)...

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BILD 2 Homework #2 5/13/08 1) What are some of the innate defenses that protect our body from invading microorganisms? First, there are barriers to invading microorganisms, such as the skin itself, mucous membranes and mucous secretions, and the pH of the stomach and the skin. Second, many niches of our body are already occupied by the natural flora present on our body and this prevents new organisms from establishing a foothold. Third, if a pathogen manages to invade the body, phagocytic cells recognize common surface features of pathogens and ingest them. These common surface features of pathogens also serve to activate the complement system, which forms pores in microbes and causes them to lyse. Finally, invading microorganisms that are sensed by phagocytic cells or other cells of the innate immune system trigger an inflammatory response; this response summons other phagocytic cells to destroy the pathogens, activates these phagocytic and other immune system cells, and impedes the pathogens from spreading to new body sites. 2) What activities of our innate defenses help to trigger an acquired immune reaction? The phagocytotic activities of dendritic cells and macrophages help to trigger an acquired immune reaction. Once ingested by these antigen presenting cells, fragments of the foreign antigen are bound to Class II MHC molecules that bring the antigen fragment to the surface of the cell. These fragments are recognized by the T cell receptor on the surface of helper T cells, and the binding in this interaction is enhanced by the CD4 surface receptor on the helper T cells. Helper T cells proliferate and proceed to secrete several different cytokines that stimulate other lymphocytes such as cytotoxic T cells to actively destroy infected cells and B cells to secrete specific antibodies against the foreign invaders, inducing their elimination. 3) How do vaccinations work to protect us against pathogens?
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Answers-Homework2_000SP08 - BILD 2 Homework #2 5/13/08 1)...

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