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Immune System Professor Andrea Garrison Biology 11 Illustrations ©2010 Pearson Education, Inc. Immune System • Function = defend against infectious disease and other “invaders” that can cause harm – Includes pathogens • Viruses and micro-organisms with potential to cause disease – Includes toxins and other substances that can harm us Immune System 2 Immune System Involves Three Lines of Defense Immune System 3 Immune System Involves Three Lines of Defense Immune System 4 Immune System Involves Three Lines of Defense Immune System 5 Immune System • Innate Defenses • Adaptive Defenses – Also called Non-Specific Defenses – Respond to any invader – Also called Specific Defenses – Respond to very specific types of invaders immune system after exposure • e.g., polio virus Immune System 6 Immune System Involves Three Lines of Defense Immune System 7 Innate (Non-Specific) Defenses • Operate without previous exposure to pathogen – External defenses (barriers to invasion) • Prevent pathogens from getting into body • Work for most pathogens in most situations – Internal defenses • Destroy pathogens that get through barriers Immune System 8 External Innate Defenses • Skin • Mucous membranes – Mucus contains lysozyme • Breaks down bacterial walls • Tears, saliva, sweat contain lysozyme • Gastric fluid contains lysozyme • Microbes – Outcompete pathogens Immune System 9 When External Innate Defenses Fail. . . Internal Innate Defenses • White Blood Cells – Phagocytic cells • Engulf foreign cells or molecules/debris from dead cells • Alert adaptive defense system Immune System 10 Internal Innate Defenses • White Blood Cells – Natural killer cells • Recognize virus-infected & cancerous cells • Release chemicals to kill them Immune System 11 Internal Innate Defenses • Defensive proteins – Interferon • Produced by virus-infected cells • Bind to receptors on healthy cells • Trigger production of antiviral proteins by healthy cells Immune System 12 Internal Innate Defenses • Defensive proteins – Complement proteins • Attach microbes – Coat surface making job easier for phagocytes – Tear holes in microbe membranes Immune System 13 Internal Innate Defenses • Inflammatory response – We see it all the time – Don’t recognize its value Immune System 14 Inflammatory Response Immune System 15 Inflammatory Response Swelling, redness, warmth Immune System 16 Inflammatory Response Swelling, redness, warmth Immune System 17 Fever • May occur with inflammation or an infectious disease • Pyrogens – Released by some bacteria – Released by white blood cells in response to infection – Released by severely damaged cells – Brain responds by creating environment too hot for viruses and bacteria to reproduce well Immune System 18 Immune System Involves Three Lines of Defense Immune System 19 Adaptive (Specific) Defenses • Respond to specific types of invaders after exposure Immune System 20 Adaptive Defenses • All cells and molecules have markers allowing them to be recognized • “Self” markers are called MHC markers • “Non-self” markers are called antigens – Your MHC markers are antigens to anyone else Immune System 21 Adaptive Defenses • Response to antigens – Lymphocytes (type of white blood cells) • B cells complete development in bone marrow • T cells complete development in thymus gland – Travel to lymph nodes and other lymphatic organs – Also reside in blood Immune System 22 Adaptive Defenses • Response to antigens – B cells and T cells have antigen receptors in their cell membranes • Bind to specific antigen based on shape – B cells and T cells have receptors for almost every possible antigen • Lie in wait for that antigen to invade body • Only few cells with each receptor shape • Most will never be used Immune System 23 Adaptive Defenses • Humoral Immune Response • Cell-mediated Immune Response – Also called antibodymediated response – B cells – Protect against invaders not yet in cells • In blood • In tissue outside cells – T cells • Helper T cells • Cytotoxic T cells – Protect against body’s own cells that pose danger • Invaded by pathogen • Cancerous Immune System 24 Adaptive Defenses • Humoral Immune Response • Cell-mediated Immune Response – Primary immune response – Primary immune response • Gets you well • Gets you well – Secondary immune response – Secondary immune response • Keeps you from getting same disease twice • Keeps you from getting same disease twice Immune System 25 Humoral Immune Response • B cell response to antigens – B cells with correct receptor for antigen will make an antibody with the complementary shape to the antigen Immune System 26 Humoral Immune Response • Antibody binds to antigens – Antibody-antigen complex triggers destruction • Marks invader for phagocytes • Physically blocks its entrance to cells • Triggers complement proteins Immune System 27 Building Humoral Immune Response • Initially only a few of each type of B cells – A few B cells produce antibodies to invader • Once the B cells w/correct antibody are found they divide rapidly – Some short-lived cells produce large numbers of antibodies to fight invader – PRIMARY RESPONSE – Some cells become memory B cells to protect against invasion a second time – SECONDARY RESPONSE Immune System 28 Initially only a few of each type of B cells, so very few antibodies Immune System 29 Once the B cells w/correct antibody are found they divide rapidly Immune System 30 Antibody producing effector B cells Immune System Memory B cells protect against later invasion 31 Humoral Immune Response • Primary response – Takes 10-14 days to build response – Short-lived effector B cells produce antibodies – Antibodies destroy invader free in bloodstream or lymphatic system • Secondary response – Memory B cells are produced that live a long time and fight infection immediately the next time you are invaded by same invader Immune System 32 Cell-Mediated Immune Response • Body cell response to invasion – Cell binds antigen to MHC marker and displays complex on cell membrane Immune System 33 Cell-Mediated Immune Response • Cytotoxic T cell response to MHCantigen display – Cytotoxic T cells with correct receptor for antigen will bind to infected cells displaying the MHC-antigen complex Immune System 34 Cell-Mediated Immune Response • Cytotoxic T cell response to MHCantigen display – Cytotoxic T cells with correct receptor for antigen will bind to infected cells displaying the MHC-antigen complex – Cytotoxic T cells kill infected cell Immune System 35 Building Cell-Mediated Immune Response • Antigen presented by phagocyte triggers two types of T cells (with correct receptor) to divide and fight invader –PRIMARY RESPONSE – Cytotoxic T cells • Kill infected cells – Helper T cells • Assist cytotoxic T cells and B cells • Some cells become memory T cells to protect against invasion a second time – SECONDARY RESPONSE Immune System 36 Cell-Mediated Immune Response • Primary response – Takes 10-14 days to build response – Cytotoxic T cells destroy infected cells • Secondary response – Memory T cells are produced that live a long time and fight infection immediately the next time you are invaded by same invader Immune System 37 Function of Helper T Cell • Helper T cells critical in adaptive immune response • Helper T cells bind to antigen presented by phagocyte • Helper T cells stimulate division of correct B cells and cytotoxic T cells, as well as memory B cells and memory T cells Immune System 38 Activation of Helper T Cell Immune System 39 Activation of Helper T Cell Immune System 40 Activation of Helper T Cell Immune System 41 Activation of Helper T Cell Immune System 42 Role of Activated Helper T Cell Immune System 43 Adaptive Immune Response – Primary and Secondary Cytotoxic T cells Memory B cells act fast if another invasion Memory T cells act fast if another invasion Immune System 44 Adaptive Immune Response Which type of lymphocyte is attacked by HIV? Immune System 45 Adaptive Immune Response Which type of lymphocyte is attacked by HIV? Helper T cells!!! Immune System 46 Adaptive Immune Response Which type of lymphocyte is attacked by HIV? Helper T cells!!! Both the humoral immune response and the cell-mediated immune response are destroyed! Immune System 47 Using Our Knowledge of the Immune System • Vaccinations – Use harmless “dead” or weakened pathogen – Stimulate primary response • Body may act “sick”—no pathogen – Stimulate secondary response – May require booster • Increase antibody levels sufficiently to fight invader quickly Immune System 48 Immune System Disorders • Allergies – Immune reaction to harmless substance – First exposure develops antibodies • Bind to body’s mast cells – Produce histamines, minor response – Second exposure triggers large number of antibodies • Histamines released – Blood vessels dilate, leak » Itchy eyes, tears, runny nose Immune System 49 Immune System Disorders • Autoimmune diseases – Body’s cells don’t recognize “self” markers • • • • Rheumatoid arthritis Lupus Insulin dependent diabetes Multiple sclerosis Immune System 50 Immune System Disorders • Immunodeficiency diseases – Severe Combined Immunodeficiency (SCID) • Very low levels of B and T cells • Require protection or bone marrow transplants Immune System 51 Immune System Disorders • Immunodeficiency diseases – Severe Combined Immunodeficiency (SCID) • Very low levels of B and T cells • Require protection or bone marrow transplants – Acquired Immunodeficiency Syndrome (AIDS) • • • • Caused by HIV Has killed >30 million people worldwide Destroys helper T cells Susceptible to opportunistic pathogens Immune System 52 Immune System Disorders • HIV – Patients susceptible to diseases healthy people easily fight – Syndrome • Lots of different diseases can attack patient – Symptoms • Little to none at first—flu-like, night sweats, fever • Long latent period • Opportunistic infections Immune System 53 Immune System Disorders • HIV – Disease of blood – Transmission • Body fluids • Sex, illegal drug use (hypodermic needles), mother to child, very occasionally blood transfusion • Virus dies quickly upon contact with air Immune System 54 Immune System Disorders • HIV – Protection • Don’t do drugs • Don’t have multiple sex partners – Monogamous relationship – Test if either partner previously sexually active • Use of latex condoms reduces risk (not 100%) • Infected pregnant women should get treatment • Infected mothers should not breast feed Immune System 55