Transcript The Immune System

What is the Immune System?
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The immune system is a complex network of cells and organs throughout the body
working together to protect the body from infection.
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The immune system uses both specific and nonspecific defense mechanisms to
detect and destroy pathogens, or disease-causing agents.
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The organs involved with the immune system are called the lymphoid organs, which affect growth,
development, and the release of lymphocytes, which are small white blood cells that are mainly
responsible for carrying out the activities of the immune system.
There are three lines of defense: the first 2 are nonspecific and the last 1 is specific.
When pathogens do invade your body, the immune system protects it from
possibly harmful substances by recognizing and responding to antigens, which are
proteins on the surface of cells, viruses, bacteria, and fungi
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Even though your own cells have antigens, the immune system has learned to recognize them as
normal and not react to them.
First Line of Nonspecific Defense
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The body’s surface defenses: the skin and mucous membranes, protect you against
all antigens thus making it your first line of nonspecific defense.
Skin- The skin is a nearly impenetrable barrier reinforced with chemical weapons
that keeps most invading pathogens from entering the body. The skin’s surface is
also acidic due to oil and sweat, so pathogens are unable to form on the skin, and
the sweat contains the enzyme lysosome, which digests bacterial cell walls.
Mucous Membranes- These are layers of epithelial tissue that produce mucus.
They line the digestive system, nasal passages, lungs, respiratory passages, and
reproductive tract. Mucous membranes can be used to trap pathogens before they
can reach the lungs and reproduce. Mucus can also be swallowed in the
esophagus into the stomach where the trapped pathogens are digested by acids
and enzymes.
Second Line of Nonspecific Defense
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Inflammatory Response- A cut or scrape in skin creates an entrance for pathogens.
Infected cells release chemicals called histamine, which cause local blood vessels
to dilate, increasing blood flow to the area. This brings white blood cells to the
infected area to attack the pathogens, causing swelling and redness around the
infected area. This results in the whitish liquid pus that comes out, which is
actually white blood cells, dead cells and dead pathogens.
Temperature Response- the body raises its body temperature when fighting
pathogens about several degrees about 37 degrees Celsius. This is what a fever is,
a common symptom of illness showing that the body is fighting an infection. This is
helpful as pathogens can’t grow well under high temperatures, however, a very
high fever can be dangerous as it can destroy important cellular proteins.
The Immune Response
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The third line of specific defense consists of a B cell and T cell response working
together simultaneously to combat specific invading pathogens.
The first step is that infected cells display viral antigens on their surfaces, where
macrophages then engulf the virus and display the viral antigens. Receptor
proteins on helper T-cells then bind to the antigens, causing the microphages to
release interleukin-1, which activate helper T-cells. The helper T-cells then activate
cytotoxic T-cells and B-cells, and also release interleukin-2, which form plasma
cells that make many antibodies. The antibodies then bind to the pathogen and
mark the virus for destruction, thus making them easily identified and destroyed
by macrophages. Receptor proteins on cytotoxic T-cells then bind to the viral
antigen by the infected cells. That way, any other cell that has traces of that
specific virus will be immediately destroyed by cytotoxic T-cells.
Lymph nodes
Lymph nodes are oval-shaped organs that act as “homes” to immune cells such as T, B and NK
(Natural Killer) Cells. These nodes are distributed through out the body, and filter out foreign
particles from the blood stream. (I.E dead/dying cells, parasites, etc.) Lymph nodes
contain lymph fluid, which is densely packed with lymphocyte and macrophages. Lymph nodes
Swell under specific conditions, ranging from a minor throat infection to cancer, due
to an increase of blood flowing through the node, and an increases in immune cells within the
node. Lymph nodes detect antigens and create corresponding antibodies to combat the invader.
Humans have around 500-600 nodes spread throughout the body, with nodes being most
concentrated in these parts of the body.
Lymphatic Vessels make up a system that transports lymph fluid similar to how veins and arteries
Transport blood. Unlike veins and arteries, however, the lymphatic system is an open system, and
has no central pump. Instead, because the vessels are composed –in part- of smooth muscle,
contraction of these muscles cause lymph to flow. Lymphatic vessels typically flow away from
body tissue, towards lymph nodes, and eventually to either the “right lymphatic duct”, or the largest
lymph vessel in the body: The Thoracic Duct. Lymph vessels act as reservoirs substances including
plasma and cells that have leaked from the vascular system. They transport lymph fluid back from
the tissues to the circulatory system. Lymph vessels also regulate Interstitial fluid- a fluid which
bath cells, provides nutrients, and helps remove waste. Lymph vessels help regulate the fluid,
keeping it from accumulating, which can cause swelling, and conditions such as edema
Bone marrow plays an important role in the immune system, as it not only creates blood cells, but
immune cells as well. The bone marrow is where immature cells develop into matured cells, ready
perform whatever task they were assigned. Because marrow has many stem cells, it is very flexible
in the cells that it is capable of producing. These cells include the lymphocyte cells: T-cells, B-cells
Natural killer cells, and most all of their variants (such plasma cell, which is a B cell which
specializes outside of the marrow).
Vaccines
• a vaccine is a preparation made to produce immunity to a
disease or other virus by stimulating the production of
antibodies.
• vaccines include killed or weakened bacteria, and other
disease causing organisms
• most vaccines are given through injection, but some are
given by mouth or nasal spray
How Vaccines Work
• a vaccine is like a pathogen-imposter: it looks like
a certain bacteria or virus to the immune system
but doesn’t make the body sick
• Pathogens are covered with antigens, so when you are given a
vaccine, it gives your immune system a similar antigen found on
the pathogen that you are trying to protect yourself against, so
the next time the virus enters the body, the body can respond to
it faster, and stronger since it is the secondary response
• Sometimes we receive booster shots to remind the immune
system how to defend against these viruses
1. When an APC finds the vaccine antigen, it ingests the invader,
and displays a piece of the antigen on its surface
2. The APC’s travel to where immune cells cluster, Naïve T calls
recognize the antigen as foreign and become active
3. Naïve B cells react to the vaccine antigen when it enters the
body
4. B cells mature into Plasma b cells and to produce antibodies
5. The antibodies are released, and then attach to the antigen
6. The next time the virus enters the body, the Killer T cells
responds and kills the virus
Diseases Vaccines Protect Against
• Some of the most common kinds of vaccines used to
protect against diseases are: Chicken Pox, H1N1, Hepatitis
a, Hepatitis B, TDAP, and Varicella
Bibliography
The Immune System. The Ohio State University. 11 May 2013
http://medicalcenter.osu.edu/patientcare/healthcare_services/infectious_diseases/im
munesystem/Pages/index.aspx
Immune Response. MedlinePlus. 11 May 2013
http://www.nlm.nih.gov/medlineplus/ency/article/000821.htm
How Vaccines Work. The History of Vaccines. 11 May 2013
http://www.historyofvaccines.org/content/how-vaccines-work
Vaccines. World Health Organization. 11 May 2013
http://www.who.int/topics/vaccines/en/
Dr. Oz: The 4 vaccines everyone should have. Examiner.com. 11 May 2013
http://www.examiner.com/article/dr-oz-the-4-vaccines-everyone-should-have
Rabbledev. “Immunize For Good - How Vaccines Work.” Youtube. Web. 16 Nov. 2010
Holt Rinehart and Winston. Holt Biology California. Austin: Houghton Mifflin School,
2007.