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The Immune System

The basic functions of the three defensive lines in the Immune System

Matthew Mikrut

on 18 April 2010

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Transcript of The Immune System

The Immune System's Three Lines of Defense
By Matthew Mikrut The First Line of Defense The First Line is non-specific, thus meaning it doesn't distinguish any specific pathogens. The first line of defense comprises of the skin, sweat glands, saliva, tears, mucus, stomach acid and other enzymes. The skin's formation of durable dead skin cells protects pathogens from entering Sweat, saliva, tears, and nostrils all obtain Lysozyme, which is an enzyme that penetrates through bacterias' cell wall Mucus in the trachea prevents pathogens from entering because of its adherent qualities, thus meaning the pathogens would stick to the mucus and it would obstruct its journey down the body. Cilia, little hairs that move mucus up, mobilizes these pathogens up to the pharnyx to be swallowed. Subsequently, stomach enzymes would annhilate pathogens. The Second Line of Defense Quite frequently, pathogens will prevail past the first line of defense. However, the second line of defense, also non-specific, would further try to obliterate pathogens. This is where the white blood cells are introduced in the immune system. These white blood cells include macrophages, neutrophils, natural killer cells, and mast cells When pathogens get through the first line, chemical alarms release an inflammatory response. An inflammatory response is a nonspecific defense depicted by swelling, pain, and redness. An example is when a pin is pricked through the skin and mast cells come quickly. Mast cells release a chemical called histamine which dilates blood vessels in the damaged area. Thus, more blood flows through that area. Afterward, macrophages and neutrophils, white blood cells that consume pathogens by phagocytosis, arrive to engulf pathogens. Their difference is that macrophages solely consume the pathogens, but neutrophils release a bleach-like chemical to both destroy the neutrophil itself and the pathogen. In addition, when a pathogen attains the contents of a cell, an enzyme called interferon is realeased from the infected cell. The cell the interferon originated from may be completly infected, but the inerferon would warn other cells to produce proteins to defeat the invading pathogens Furthermore, some cells in the body will be completly taken over by pathogens. Therefore, the natural killing cells come to kill cells infested with the pathogen. They puncture through their membranes and insert chemicals to kill it. The Third Line of Defense If the pathogen manges to surpass the first two defenses, it must encouter the third line of defense, which unlike the first and second line, is targeted. This means that it targets distinct pathogens in the body. The third line of defense includes macrophages, helper T cells, cytoxic T cells, B cells, plasma cells, and memory cells. Like the second line of defense, the third line utilizes macrophages. In the third line, the macrophages consume the pathogens through phagocytosis, and then the macrophages display the pathogen's antigens on its membrane. Then the helper T cells arrive and hook on to the macrophage's antigens. Subsequently, they create responses and summon cytoxic T cells and B cells. T cells and B cells are lymphocytes, or cells that travel through lymphs. Then the cytoxic T cells kill infected cells using an enzyme called perforin. They do this by binding to antigens on the infected cells and inserting the perforin which punctures through their membrane. Then the perforin causes the cell to burst open and become decimated. On the contrary, the B cells also contribute significantly to the third line. They recognize specific antigens by their antibody recepters. The B cell proliferates and becomes a plasma cell. The plasma cells secrete antibodies. These antibodies latch on to the pathogens' anigens and hinder its capabilites. After the pathogens are completly defeated, the remaining B and cytoxic T cells become memory cells. Memory cells remember a pathogen and rapidly proliferate to defeat a pathogen when it returns. In the third line, there are primary and secondary responses. Ultimatly, the primary response is slow because it needs sufficient time for lymphocytes to form and defeat the pathogen. However, the secondary response to a pathogen is much faster because there are B and T memory cells that could easily defeat it
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