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The Immune System

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on 18 April 2010

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Transcript of The Immune System

The Immune system First Line of Defense second line of defense Third line of defense Non-specific Defenses consists of mainly
skin, sweat and oil glands,
saliva, tears, mucous membranes,
stomach acids and enzymes Skin contains sweat and oil
glands. These glands secrete
acids and oils that prevent
the growth of many micro-
organisms, acting as a
chemical barrier. picture of a oil and sweat gland
in the surface of a skin The outerlayer of the skin is comprised of
tough, dead cells that most bacteria and
other organisms cannot penetrate. Also
this layer of skin is constantly shedding,
which makes it difficult for bacteria to
embed in it and grow GWB perspiring sweat contains lysozyme,
an enzyme that breaks down the cell walls
of many bacteria Saliva and tears contain lysozyme,
which helps protect the mouth and
eyes from bacterial invasion Digestive and respiratory passageways are lined with mucous membranes, another barrier. Mucus in the trachea, for example, creates a sticky barrier that traps microorganisms. Cilia move these trapped particles up to the pharynx where they are swallowed. Then, stomach acids and enzymes help to destroy the pathogens, as well as many other microorganisms in your food and drink. Cilia damaged by a flu virus Internal Non-specific Defenses When pathogens pass your first line of defense, invaders meet your second line of defense. These include certain pathogen-destorying white blood cells, the inflammatory response and certain specialized proteins. They do not single out specific pathogens so they are identified to be Non-Specific. White blood cells roam through the bloodstream,
interstital fluid and lympatic system attacking invaders.
Some, such as macrophages and neutrophils, destroy
microorganisms through phagocytosis
(meaning "cellular eating"). Macrophages are found
mainly in interstitial fluid. When a macropage encounters
an invading pathogen, the macrophage engulfs the
organism much as an amoeba ingests food. A Macrophage going through Phagocytosis Neutrophils are smaller and more numerous in the body
and also kill by phagocytosis. once the pathogen is inside
the neutrophil, it releases a chemical that kills the invading
pathogen, however this chemical also kills the neutrophil. The most important thing is the white blood cell's
ability to identify which structures to attack and
leave alone by certain proteins and carbohydrates
n the surface of an invading pathogen.
Recognizing these "foreign" molecules triggers
the cell's response. Natural Killer cells are found in the bloodstream
and do not attack pathogens directly or kill by
phagocytosis. Instead, they recognize body cells
that have been infected by a virus and kill them
by releasing a chemical that depletes a infected
cell's membrane. They also kill cancer cells
before they form tumors. An NK cell attacking a tumor. When pathogens invade through the skin, certain cells release a variety of chemical alarms that signal the inflammatory response. A nonspecific defense characterized by redness, heat, swelling and pain. When pathogens trigger the inflammatory response, histamine is released by mast cells into nearby blood vessels that cause them to dilate. More blood flows to the area, vessels become more porous allowing blood plasma to leak into the interstitial fluid. Other chemicals attract white blood cells and phagocytes to the area were they pass through leaky blood vessel walls into the interstitial fluid. This rapid increase of blood flow and white blood cell activit yproduces this swelling and redness. The inflammatory response includes removing pathogens and cleaning injured tissues. When the inflammatory response reacts with the circulatory system because of pathogens, a fever might occer and can be damage. Because if the temperature is very high, it can destroy protein. But a moderate fever can be an addition to defense because of stimulation of phagocytosis and the stop of growth for many kinds of micro organisms. However there are these specialized proteins called
interferon which attack invaders directly or block
their reproduction system. The infected cell may die,
but its interferon reaches healthy cells in the area,
stimulating them to produce proteins that interfere
with virus production. This is effective against many
kidns of viruses, thus making it nonspecific. Interferon
are effective against viruses that cause the flue
and the common cold. The Targeted Defense Supporting the nonspecific defenses is your body's third line of defense, the immune system. This system recognizes and defendes against specific pathogens, cancer cells and certain chemicles. The third line is therefore a specific, or targeted defense. To accomplish this, the immune system must be able to distinguish between its own body cells and intruders. When non-self cells or other intruders are identified, the immune system launches a customized response. Immunity means that your body is resistant to
the pathogen that causes a specific disease. To
be resistent in the first place requires to be
infected by that specific pathogen. An antigen is a large molecule, usually
a protein that provokes a immune response. Antibodies are proteins found on the surface of certain white blood cells, or in blood plasma, that attach to particular antigens. They are Y shaped that prevent most bacteria and infected cells from receiving any source of nutrients. Antibodies have rabbit-ear antennae that
recognize a specific antigen. It attaches
itself to the invading particle and attatch
to the familiar "knobs" By binding to these markers, the antibodies render viruses useless because of their inability to attach to a host cell. For bacteria, it may make it useless and tag it for phagocytes to kill. They also clump pathogens together making it easier for phagocytes to destroy. They can also cause the immune system to release chemicals to attach to viral surfaces or bacterial membrances. White blood cells that recognise specific
invaders are called lymphocytes The body destroys lymphocytes with clashing antigen markers to avoid confusion when theres pathogens invading. B cells are madein the Bone marrow and depending wether they go to the thymus, they go to the b cells and the t cells. B cels play a key role in humoral immunity while T cells play the major role in cell-mediated immunity. B cells defend primarily against bacteria and viruses that are found outside of cells in body fluids. B cell containing matching antigen receptors bind to the antigens of the pathogen activating the B cell. This makes the B cell reproduce rapidly into billions of B cells that are capable into forming a plasma cell, which produces and secretes antibodies specific to the antigen that activated the original B cell. Plasma cells then are carried through sites of infection thgroughout the body. This is called humoral immunity. T cells work by directly attacking host cells that contain multiplying bacteria or viruses. Since T cells attack other cells, they produce a type of immunity called cell-mediated immunity. Each T-cell has receptors for a specific antigen. When this pathogen infects a body cell, pthe antigens are displayed on the surface of the body cell. Antigens bind to the receptors of the matching T cell which ctivates it. It then divides into million other T cells. Cytotoxic T cells then attack infected cells by binding on their membranes and poking holes into them and secretes perforin into them. The Cell breakes open and dies. Both humoral and cell-mediated immunity get a boost from a particular type of lymphocyte called helper T cells. The antigen displaying cells that helper T cels recognise are macrophages, the white blood cells that eat pathogens by phagocytosis. Helper T cells respond to alerting macrophages by secreting chemicals that signals cytotoxic T cells and B cells. After all this, all defending cells die except memory cells which contain the antigens of the previous pathogens so they can react quickly whenever the same pathogen attacks. By Ethan Cheng
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