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Immune Defense against Disease

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What is an infectious disease? Disease-producing agents such as bacteria, protozoans, fungi, viruses, and other parasites are called pathogens. (NOT all microorganisms are pathogens) Main sources of pathogens are soil, contaminated water, and infected animals, including other people.

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Reservoirs of pathogens Pathogens are some causes of infectious diseases.

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Transmission of disease Pathogens can be transmitted to a host from reservoirs in four main ways: by direct contact, by an object, through the air, or by an intermediate organism called a vector.

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Transmission of disease II The common cold, influenza, and STDs are spread by direct contact.

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Transmission of disease III Bacteria and other microorganisms can be present on nonliving objects such as money, toys, or towels. Transmission occurs when people unknowingly handle contaminated objects.

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Transmission of disease IV Airborne transmission of a disease can occur when a person coughs or sneezes, spreading pathogens contained in droplets of mucus into the air.

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Transmission of disease V Diseases transmitted by vectors are most commonly spread by insects and arthropods. Malaria and the West Nile virus are transmitted by mosquitoes. Lyme disease and Rocky Mountain spotted fever are diseases that are transmitted by ticks. Flies also are significant vectors of disease.

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What causes disease symptoms? When a pathogen invades your body, it encounters your immune system. If the pathogen overcomes the defenses of your immune system, it can metabolize and multiply, causing damage to the tissues it has invaded, and even killing host cells.

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Host damage by viruses and bacteria Viruses - are they alive? Viruses are exceptions to the cell theory A virus is not a cell. Viruses are made of two chemicals, protein & nucleic acid, but have no membranes, nucleus, or protoplasm Viruses appear to be alive when they reproduce after infecting a host cell

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Host damage by viruses and bacteria Most of the damage done to host cells by bacteria is inflicted by poisonous toxins. These toxins can inhibit protein synthesis in the host cell, destroy blood cells and blood vessels, produce fever, or cause spasms by disrupting the nervous system.

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Patterns of Diseases Some diseases, such as typhoid fever, occur only occasionally in the United States. On the other hand, many diseases are constantly present in the population-endemic disease. (Ex., the Common cold, rhinoviruses)

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Treating Diseases 1 Way -Treating diseases with antibiotics: An antibiotic is a substance produced by a microorganism that, in small amounts, will kill or inhibit the growth and reproduction of bacteria. Note that antibiotics have NO impact on viruses, only bacteria! Your body also has its own built-in multi-layer defense system the immune system that works to keep you healthy.

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Lines of defense 1st line: Barrier defense broad, external defense walls & moats skin & mucus membranes 2nd line: Non-specific defense broad, internal defense patrolling soldiers phagocyte (eating) WBCs

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Lines of defense 3rd line: Immune System Action specific, acquired immunity elite trained units lymphocyte WBCs & antibodies B & T cells

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Innate Immunity The bodys earliest lines of defense against any and all pathogens make up your nonspecific, innate immunity.

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Nonspecific defense 1 1st line of defense: Skin Intact skin is a formidable physical barrier to the entrance of microorganisms Lining of trachea: ciliated cells & mucus secreting cells

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Nonspecific defense 1 1 st line of defense: Body secretions mucus traps many microorganisms. Sweat, tears, and saliva all contain the enzyme lysozyme, which is capable of breaking down the cell walls of some bacteria.

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Nonspecific defense 2 2 nd line of defense: Inflammation(Inflammatory response) characterized by four symptomsredness, swelling, pain, and heat; histamine released causes blood vessels in the injured area to dilate,(redness) which makes them more permeable to tissue fluid. Fluid that leaks from the vessels helps the body destroy toxic agents and restore homeostasis (swelling, pain, & heat)

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Nonspecific defense 2 2 nd line of defense: After a few days, infected tissue harbors a collection of live and dead white blood cells, multiplying and dead pathogens, and body fluids called pus. Pus formation usually continues until the infection subsides. Eventually, the pus is cleared away by macrophages. Pus Phagocytes Swelling occurs Tissue fluid moves into injured area

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Nonspecific defense 2: Fever 2 nd line of defense: When a local response is not enough a full body response to infection raises body temperature. The higher temperature helps in defense as it slows growth of pathogens, helps macrophages, and speeds up repair of tissues.

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Nonspecific defense 3 2 nd line of defense: Phagocytosis of pathogens - white blood cells that destroy entire pathogens by surrounding and engulfing them. Macrophages are white blood cells that provide the first defense against pathogens that have managed to enter the tissues. Macrophage eating bacteria

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Phagocytes yeast macrophage bacteria white blood cells that eat

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Nonspecific defense 4 2 nd line of defense: Phagocytosis of pathogens If the infection is not stopped by the tissue macrophages, another type of phagocyte, called a neutrophil, is attracted to the site. If the infection is not stopped by tissue macrophages and neutrophils then Monocytes are introduced.

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Nonspecific defense 5 2 nd line of defense: Protective proteins Interferon is a group of proteins that protect cells from viruses. Complement: help attract phagocytes to foreign cells and help destroy foreign cells. Natural Killer cells: type of white blood cell that destroy the body's own infected cells, and may attack cells that form tumors.

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Nonspecific defense 5

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The lymphatic system 2 nd line of defense: The lymphatic system becomes a crucial battleground during infection. It is a network of lymphatic vessels and organs. It returns tissue fluid to the circulatory system. It fights infections. Lymph nodes are key sites for fighting infection. They are packed with lymphocytes and macrophages.

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The lymphatic system

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Acquired Immunity Acquired Immunity d efending against a specific pathogen by gradually building up a resistance to the pathogen. This acquired immune response enables these white blood cells to inactivate or destroy the pathogen. Acquired immunity involves the production of two kinds of immune responses: antibody immunity and cellular immunity: your 3 rd line of defense

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Acquired Immunity 3 rd line of defense: SPECIFIC IMMUNITY IMMUNE RESPONSE: a recognition system that distinguishes self from non-self. responds to foreign molecules called antigens Stimulates the body to make antibodies: specific defensive proteins which help to counter antigens in various ways.

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How are invaders recognized? Antigens chemical name tags on the surface of every cell Label all cells as self vs. invader disease-causing bacteria disease-causing virus one of your own cells antigens say: I belong here antigens say: I am an invader

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Lymphocytes 3 rd line of defense: Lymphocyte type of white blood cell that carry out the immune response. Two kinds of lymphocyte: B cells secrete antibodies that attack antigens (antibody immunity) T cells attack cells infected with pathogens (cellular immunity) B lymphocyte

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B cells & antibodies 3 rd line of defense: B cells white blood cells that attack invaders in blood mature in Bone marrow i.Patrolling B cells make antibodies against invader immediately ii.Memory B cells remembers invader make antibodies quickly the next time; protects you from getting same disease more than once

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3 rd line of defense: Antibodies Proteins made by B cells that tag invaders in the blood so macrophages can eat them. tag says this is an invader gotcha! biological handcuffs antibody attaches to antigen of invader Antibodies macrophage eating tagged invaders Invading germs tagged with antibodies Y Y Y Y Y Y Y B cells releasing antibodies Y Y Y Y Y Y Y Y Y Y Y Y Y Y

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Antibody Immunity 3 rd line of defense: An antibody molecule has antigen-binding sites specific to the antigen. Antibodies do not possess the power to destroy antigens directly, but antibodies tag and identify antigen-marked cells for destruction by a variety of mechanisms.

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B cells immune response invader (foreign antigen) Y Y Y Y B cells Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y reserves memory B cells Y Y Y Y Y Y Y Y Y Y Y Y Y B cells release antibodies patrol blood forever recognition 10 to 17 days Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y

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T cells 3 rd line of defense: T cells mature in the Thymus Helper T cells sound the alarm for rest of immune system Killer T cells destroy infected body cells Memory T cells remembers invader & reacts against it again quickly Wheres that?

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Attack of the Killer T cells 3 rd line of defense: Killer T cells destroy infected body cells T cell binds to invaded cell & secretes Perforin Perforin punctures cell membrane of infected cell cell bursts (lysis) Perforin: punctures invaded cell membrane T-cell membrane Killer T cell I-cell membrane invaded cell vesicle

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Cellular Immunity Pathogen engulfed by Macrophage Displays antigens on surface and stimulates T cell Helper T cell Stimulates Cytotoxic T cell Attacks infected cell Cytotoxic T cell Foreign antigen Infected cells Perforin Infected cell lyses

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Immune response invader invaders in bloodinvaders infect cells B cellsT cells macrophages helper T cells patrolling B cells memory B cells memory T cells killer T cells Y Y Y Y YY Y Y antibodies Y Y Y skin invaders in body Y Y Y Y YY Y Y antibodies Y Y Y

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Passive and Active Immunity Acquired immunity to a disease may be either passive or active.

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Passive Immunity Passive immunity: short term, antibodies passed on, not stimulated by antigens. acquired naturally by placenta or breast milk artificially acquired by a vaccine

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Active Immunity Active: long term, conferred by actual encounter with infection (naturally acquired) or vaccine (artificially acquired). Vaccine substance consisting of weakened, dead,or parts of pathogen or antigen that when injected, stimulates the immune system.

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Noninfectious disorders Genetic disorders Caused by the inheritance of genes that do not function properly. ex: sickle cell anemia, hemophilia, cystic fibrosis

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Noninfectious disorders Degenerative diseases result of a part of the body wearing out (ex: degenerative arthritis) Metabolic diseases results in an error in a biochemical pathway Cancer abnormal cell growth

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Immune System Disorders Allergies are overreactions to certain environmental antigens called allergens (ex. animal dander, dust mites, pollen) The release of histamine causes symptoms: sneezing, increased mucus production in the nasal passages, and redness. Antihistamines can relieve symptoms.

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Immune System Disorders Autoimmune diseases: the immune system also can mistakenly attack the bodys own tissues. (ex: Rheumatic fever, Type I Diabetes, Multiple Sclerosis, Rheumatoid arthritis, Lupus) Rheumatoid arthritis

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Immune System Disorders Immunodeficiency diseases: Immune components are lacking, and infections recur Ex: Acquired immune deficiency syndrome (AIDS) AIDS is result of HIV infection; HIV is NOT AIDS! HIV Replication

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AIDS HIV (Human Immunodeficiency Virus); the virus that causes AIDS. HIV is transmitted mainly in blood and semen. HIV kills helper T-cells and can lead to AIDS.

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Attacking transplanted tissue. T cells and antibodies also can attack transplanted tissue, such as a transplanted organ, that comes from a source outside new host body. Blood transfusions with wrong antigens (blood type) are attacked, leading to clotting.