the immune system what happens when we get sick? why do we get better?
TRANSCRIPT
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THE IMMUNE SYSTEM
What happens when we get sick?
Why do we get better?
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How does your body know when a substance is an invader?
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Functions of the Immune System
• 1. Recognize self vs. non-self
• 2. Destroy non-self
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Foreign Invaders
• Antigen:
– Any non-self substance capable of triggering an immune response
– An antigen can be a whole non-self cell, a bacterium, or a virus.
• Even allergens and cancerous cells
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Foreign Invaders
• Antibody:
– Protein that recognize and bind to pathogens.
– Once the body has been exposed to a pathogen, the body creates memory B cells, reducing the chance of being infected again!
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ANATOMY OF THE IMMUNE SYSTEM
• The immune system is localized in several parts of the body
– immune cells develop in the bone marrow and thymus
– immune responses occur in the secondary organs
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ANATOMY OF THE IMMUNE SYSTEM:The immune system is localized in several parts of the body
– Spleen: filters and removes old and damaged red blood cells
• removes infectious agents and uses them to activate cells called lymphocytes
– Bone marrow: tissue insides bones that produces blood cells
• B cells and T cells are types of white blood cells
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ANATOMY OF THE IMMUNE SYSTEM:The immune system is localized in several parts of the body
– Thymus: T cells mature here (learn their job)
– Lymph nodes: small organs that filter out dead cells, antigens, and other “stuff” to present to lymphocytes
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ANATOMY OF THE IMMUNE SYSTEM:The immune system is localized in several parts of the body
– Lymphatic Vessels: collects fluid (lymph) “leaked” from blood into the tissues and returns it to circulation
– Tonsils: 3 pairs masses of lymphoid tissue- helps protect against bacteria around the throat
– Appendix: “safe house” for the beneficial bacteria living in the human gut
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• Non-specific defense mechanisms:– The body’s attempt to destroy all types of foreign
invaders – General, not targeted to a specific pathogen (virus
or bacteria)
• Specific defense mechanisms:– Immune response specific for a pathogen
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There are three lines of defense against infection
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First Line of Defense:The outer layer of the body
• Goal:prevent organisms from gaining access to the body
• Details:
– Physical barriers: skin, hair
– Chemical barriers: sweat, tears, saliva, mucus, skin
• These contain enzymes that break down cell walls of many bacteria
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Second line of defense: Cells and proteins in our blood stream
• Goal: recognize, neutralize and destroy invaders inside the body• Details: inflammation and fever (swelling, redness, warmth, pain)
– Increased blood flow brings cells to fight infection• Macrophage, phagocytes, and neutrophils
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Third Line of Defense: The Immune Response
• Two types of cells are involved:
– B cells: provide immunity against antigens and pathogens in the body fluids by making antibodies• This is called humoral immunity• Vaccines cause B cells to produce antibodies
– T cells: provide defense against abnormal cells and pathogens inside living cells• This is called cell-mediated immunity
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Putting it all Together• 1. Virus infects body
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Putting it all Together2.Macrophage (WBC) eat virus and display viral antigen
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Putting it all Together• 3. White blood cell activates Helper T cell
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Putting it all Together• 4. Helper T Cells activate B cells and killer T cells
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Putting it all Together• 5. Some B cells become memory cells for future
immune response, some become plasma cells
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Putting it all Together• 6. Plasma cells make antibodies which bind to viral antigen
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Putting it all Together• 7. Antibodies attach to the virus and infected body cells, signals for their destruction
– Antibodies protect against foreign invaders
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Putting it all Together• 8. Killer T cells destroy infected body cells
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• 1. Virus infects body, cells display viral antigens• 2. Macrophages engulf virus and display viral
antigen• 3. Macrophages activate helper T cells• 4. Helper T Cells activate cytotoxic T and B cells• 5. B cells form plasma cells
– Some B cells become memory cells for immune response later on
• 6. Plasma cells make antibodies which bind to viral antigen
• 7. Antibodies attach to the virus and infected body cells, signals for their destruction– Antibodies protect against foreign invaders
• 8. Cytotoxic T cells destroy infected body cells
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HIV (Human Immunodeficiency Virus)
• Cause: – Human Immunodeficiency Virus
• Symptoms:– Fever, headache, tiredness, enlarged lymph nodes– AIDS (Acquired Immunodeficiency Syndrome)
• weight loss, fatigue, memory loss – Destroys Helper T cells (part of immune system)
• body cannot fight off illnesses caused by bacteria, other viruses, fungi, or parasites.
• Ultimately leads to death
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HIV (continued)• Treatment:
– Reverse Transcriptase (RT) inhibitors & Protease Inhibitors- stops the virus from making copies of itself
• Transmission:– sexually (orally, vaginally)– Blood (needles, or through mucus membranes)– Breast milk mother to child– NOT from kissing, touching, insects bites
• Status:– No vaccine, several medicines to prevent spread in body– Worldwide: In 2004, 40 million people living with HIV/AIDS, 5
million newly infected, and 3.1 million deaths
• Prevention:– Abstinence, Safe sex (Condoms!), avoidance or risky behaviors
associated with sex and drug use
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