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Immune system

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Tanay Venkateswaran

on 20 April 2010

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Transcript of Immune system

The Immune System The First Line: Barriers The Skin - made up of dead cells which most bacteria cannot penetrate. Also constantly sheds which prevents bacteria from embedding and growing in it. Oil and Sweat glands in the skin secrete acids and oils that prevent growth of microorganisms
Sweat, Saliva, and Mucus - Sweat, Saliva, and Mucus all contain lyzozyme which is an enzyme that breaks down the cell walls of many types of bacteria. Mucus can also trap microorganisms. Response The Second Line: Internal Specific Defenses White Blood Cells:
Macrophages and neutrophils destroy microorganisms through phagocytosis.Neutrophils also release chemicals after phagocytosis which kills the invading pathogen as well as itself.
Natural Killer cells also roam the bloodstream attacking any cells that have been infected by viruses, as well as attacking abnormal cells such as cancer cells. Inflammatory Response:
Mast cells release histamine at the site of pathogen invasion which causees nearby blood vessesl to dilate. The expanded blood vessels will increase the amount of blood flowing to the site.Vessels also become porous which increases the amount of blood plasma in interstitial fluid.This creates swelling.Other chemicals released attract additional phagocytes and other white blood cells.
The main function of inflammatory response is to remove pathogens and to clean injured tissues.
Specialized Proteins:
Interferons are produced by cells when they are invaded by viruses. Even if the infected cell dies, its interferons will reach nearby healthy cells, stimulating them to proteins that interfere with virus reproduction. The Third Line: Targeted Defense B Cells and Humoral Immunity: T Cells and Cell-Mediated Immunity: T cells are activated by macrophages carrying antigens.When activated T cells divide and multiply into cytotoxic T cells which attack cells infected with the antigen that activated it.They kill infected cells by binding to it and then poking holes in it by secreting a protein called perforin. B cells are activate by T cells. Afer activation the B cell grows and clones itself multiple times. Each cells is capable of turning into a plasma cell which produces and secretes antibodies specific to the activator antigen. The plasma cells are carried through the bloodstream to infected sites, once there they release their antibodies which paralyze the viruses. Immunity Through Memory: After you are first exposed to a pathogen and quell it, some of the B and T cells remain in your body. These cells are called memory cells. If you are exposed to the same pathogen again, your immune system can respond much quicker because of these cells. This is acheived because as soon as the second exposure happens the B cells rapidly produce plasma cells to secrete antibodies. At the same time T cells produce a large number of cytotoxic Tcells to attack infected cells. This usually happens so quick that you dont develop symptoms.
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