By Taran Virdi, Brandon Vo, and Jordan Whittaker

1. The Immune System By Taran Virdi, Brandon Vo, and Jordan Whittaker

2. What is the Immune System? • The immune system is a complex network of cells and organs throughout the body working together to protect the body from infection. • 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. • The immune system uses both specific and nonspecific defense mechanisms to detect and destroy pathogens, or disease-causing agents. • 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 • Even though your own cells have antigens, the immune system has learned to recognize them as normal and not react to them.

3. First Line of Nonspecific Defense • 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.

4. Second Line of Nonspecific Defense • 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.

5. The Immune Response • 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.

6. Structures of the Immune System Lymph nodes Lymph nodesare 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 nodescontain lymph fluid, which is densely packed with lymphocyte and macrophages. Lymph nodesSwell under specific conditions, ranging from a minor throat infection to cancer, dueto 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.

7. Lymphatic Vessels LymphaticVessels make up a system that transports lymph fluid similar to how veins and arteriesTransport 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 largestlymph 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

8. Bone Marrow 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 flexiblein the cells that it is capable of producing. These cells include the  lymphocyte cells: T-cells, B-cellsNatural killer cells, and most all of their variants (such plasma cell, which is a B cell which specializes outside of the marrow).

9. 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

10. 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 • When an APC finds the vaccine antigen, it ingests the invader, and displays a piece of the antigen on its surface • The APC’s travel to where immune cells cluster, Naïve T calls recognize the antigen as foreign and become active • Naïve B cells react to the vaccine antigen when it enters the body • B cells mature into Plasma b cells and to produce antibodies • The antibodies are released, and then attach to the antigen • The next time the virus enters the body, the Killer T cells responds and kills the virus

11. 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

12. Bibliography The Immune System. The Ohio State University. 11 May 2013 http://medicalcenter.osu.edu/patientcare/healthcare_services/infectious_diseases/immunesystem/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.