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Immunity
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Role: Defense Three major types of defense: - Physical and chemical barriers - Non-specific defense use various means - Specific defense: Immunity
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Physical and chemical barriers Physical barriers: - skin, mucous, flow of tears, urine, saliva, earwax, defecation, vomiting Chemical barriers: -Enzymes in the stomach, on the skin, in tears, saliva -Low pH of gastric juice, vaginal secretions -Resident bacteria
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Non-specific defenses Phagocytosis Inflammation Natural killer cells Complement system Interferon Fever
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Phagocytosis
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Inflammation
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Natural killer cells Kill cells by perforing the membrane Promote inflammatory response Especially active against viral infections and cancerous cells
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Complement system
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Interferon
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Fever Triggered by pyrogens, substances secreted by macrophages Slow down bacterial growth
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Specific defense: Immunity Two categories : -Antibody-mediated immune response (AMI) against pathogens extrernal to the cell (bacteria, fungi) -Cell-mediated immune response (CMI) against pathogens internal to the cell (virus, cancer)
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Characteristics It recognizes and targets specific pathogens or foreign substances, known as antigens It has memory It protects the entire body
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What are antigens Antigens are proteins that are foreign to a body
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What about our own cells? They have proteins on the cell membrane. These proteins define our identity and differentiate us from other beings These “self-markers” are known as the “Major Histocompatibility Complex” or MHC The immune system is able to differentiate between the two types of proteins
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The main players Macrophages B lymphocytes Killer T lymphocyte Helper T Lymphocytes (and a macrophage)
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AMI Goal: Attack external pathogens such as bacteria, fungi Cells involved: Macrophages, B lymphocytes (=B cells), plasma cells and helper T lymphocytes
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Antibodies Role: Flag the pathogen (do not kill it directly) Promote phagocytosis Five types of antibodies - IgG: in the plasma, most abundant, long life, can cross the placenta - IgM: largest, first to respond, cannot cross the placenta - IgA: in mucous membranes, external secretions, throughout body - IgD: in lymph, on B cells - IgE: on B cells, mast cells, and basophils, trigger allergic responses
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Antibody
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CMI Goal: Attack internal pathogens such as virus infected cells and cancerous cells Cells involved: Macrophages, Killer T (or cytotoxic) lymphocytes (=killer T cells), plasma cells and helper T lymphocytes
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AMI and CMI
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Primary and secondary immune response
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Types of immunization ActivePassive Natural Artificial
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Bacterial resistance to antibiotics
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Allergic reactions
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Tissue rejection Implanted organs have a high risk of rejection, since no two persons are alike (except identical twins) Cell-mediated immunity is responsible for the reaction Upon receiving an organ, a person must take antirejection medications for life
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Autoimmune disorders Lupus erythematosus: inflammation of the connective tissue Rheumatoid arthritis: Inflammation of the synovial membrane (joints) Diabetes mellitus, type I: destruction of the cells synthesizing insulin Multiple sclerosis: destruction of the sheath surrounding the axon of the nerve cells
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Ebola vs Flu vs Cold
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Human Immunodeficiency Virus
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HIV prevalence
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