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Our Immune System

How does our immune system work?

Matthew Ooi

on 19 April 2010

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Transcript of Our Immune System

Our immune System General Overview The immune system is a system of many interdependent cells that protect the body from pathogens, a.k.a.
Bacteria -

Viruses -

Parasites -

Tumors -

The First Line of Defense
(Nonspecific-Defenses) The Skin
Tightly packed cells stop any pathogens from getting through.
The top layer of the skin which is comprised of tough, dead cells which most pathogens cannot penetrate. Unless something punctures the skin, allowing pathogens to get through, which then sets the 2nd line of defense into action. The Second Line of Defense
(Internal Non-Specific Defenses) Vocab - Nonspecific Defenses - barriers that protectect the body from invaders, without specifically distinguishing each 'invader' from another sweat and oil glands act as a chemical barrier preventing bacteria growth, also sweat contains lysosome which breaks down the cell walls of bacteria Saliva contains lysozyme which helps protect the mouth from bacterial invasion Tears also contain lysozyme and it protects the eyes Mucus and cilia work together to make trap the bacteria in a sticky trap (mucus) then transport it down to the stomach (cilia) where it is dissolved by the stomach acid Macrophages - destroy bacteria through phagocytosis, in which they engulf the bacteria where lysozome breaks it down
Neutrophils - like macrophages they use phagocytosis but are more commonly found and instead of lysozyme release chemicals that kill the pathogen and the neutrophil itself
NK (Natural-Killer) Cells - Instead of using phagocytosis, NK cells go around and recognize infected body cells and kill them by releasing chemicals which pokes holes in the infected cells membrane
Interferon - produced in small quantities when a cell is infected, the interferon stimulates other cells to produce proteins that interfere with virus production Mast Cells Inflammatory Response Inflammatory Response Cells -
Mast Cells - reach the infected skin surface first, releasing histamine and notifying phagocytes and neutrophils to clean the area
The main reason for the inflammatory response is to clean out all infected tissue cells Vaccines A vaccine is a shot of a weakened or dead strain of a virus pathogen, meant to allow your body to fight it and remember the virus, so when it actually attacks it can fight the pathogen easily. The Third Line of Defense
(Humoral and Cell mediated Responses)
The Third line of defense is a specific defense, although the process is longer, the humoral and cell mediated response is alot more effictive than the first two lines of defense put together Antigens - a large molecule that, usually a protein that provokes an immune response
Antibodies - proteins that are found on the surface of certain white blood cells, that attach to antigens, y shaped the tips of each antibody is unique in that it can only bind with a specific antigen with a proper receptor. This allows antibodies to recognize and neutralize a variety of different viruses. FYI
Most bacteria, tumors, and parasites are harmless. But all viruses are! How do antibodies kill viruses?
The binding of antibodies to an antigen marker stops the virus from attaching to a host cell, halting any more infection, antibodies also make the harmless viruses clump together, which are then eaten by macrophages and neutrophils. Antibodies also may activate immune system chemicals called complement proteins that attach to viral surfaces or bacterial membranes. These proteins puncture holes in bacteria and viruses causing the pathogen to break open. Antigens and Antibodies Lymphocytes B-cells and T-cells - also known as lymphocytes, they originate in the bone marrow from stem cells and these two types of cells have different antigen receptors on them allowing them to target specific antigen markers. Although no one B-cell and T-cell are alike, this allows many different varieties of antigen receptors. These cells play a huge part in the immune system, B-cells in humoral response, and T-cells in cell-mediated responses. B-cells and Humoral Responses Antibody proteins are embedded on each B-cell and each protein is only activated by a specific type of antigen. When fighting a pathogen B-cells match the antigen markers to its antigen recepters, this activates the B-cell, it replicates itself forming millions of identicle cells, each one capable of turning itself into a plasma cell. Which produces and scretes antibodies specific to the antigen that activated the orginal B-cell. Since B-cells and antibodies primarily travel in the body fluid (or humor) the name to this response is the Humoral or body fluid response. (The B cells normally attack pathogens outside cells in the body fluid) Summary of 3rd Line of Defense T Cells and Cell Mediated Immunity T cells directly attack the host cells which are infected, thus called cell-mediated or cell attacking cell response. Like B cells, T cells are activated when a specific antigen markers bind with its antigen receptors, it then clones itself into cytotoxic T cells which then attack the cells infected cells by binding, then secreting perforin into the infected cell which opens holes and leaks out and dies. Helper T Cells Helper T cells are lymphocytes that help greatly with the activation of B, and cytotoxic T cells. Like cytotoxic T cells, they bind with the infected host cells and then display the antigens which activate the cytotoxic T cells and B cells. Primary and Secondary Immune Responses After killing the invading pathogens, the T and B cells which helped fight it off remain in your body as memory cells. These lymphocytes are triggered again when the same invading pathogens come, and the response to defeating the pathogen is much quicker. A second exposure to the same virus puts the memory cells into action, cloning large amount of B and T cells which will produce antibodies and destroy host cells defeating the pathogen in no time. END
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