Chap 15 – BYU – Flashcards
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| Innate Resistance |
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| Resistance to plant and many animal pathogens |
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| The Three Lines of Defense |
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| Non-specific: skin. phagocytosis. Specific: lymphocites, antibodies. |
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| First Line of Defense |
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| skin and mucous membranes of the respiratory, digestive, urinary, and reproductive systems |
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| Skin |
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| Epidermis Epidermal dendritic cells |
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| Epidermal dendritic cells |
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| Also termed Langerhans cells Phagocytize pathogens |
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| Dermis |
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| Contains protein fibers called collagen Give skin strength and pliability to resist abrasions that could introduce microorganisms |
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| Skin – Chemical Components of Defense |
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| Perspiration secreted by sweat glands Sebum secreted by sebaceous (oil) glands |
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| Perspiration secreted by sweat glands |
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| Salt- inhibits growth of pathogen by drawing water from their cells Lysozyme- destroys cell wall of bacteria |
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| Sebum secreted by sebaceous (oil) glands |
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| Helps keep skin pliable and less likely to break or tear Lowers the pH of the skin to a level inhibitory to many bacteria |
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| Mucous Membranes |
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| Line all body cavities open to the outside environment Two distinct layers Epithelium Deeper connective layer that supports the epithelium |
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| Skin – Chemical Components of Defense |
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| Perspiration secreted by sweat glands Sebum secreted by sebaceous (oil) glands |
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| Epithelium |
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| living Tightly packed to prevent entry of pathogens Continual shedding of cells carries attached microorganisms away |
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| Ciliary Escalator |
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| Microbial Antagonism |
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| Normal microbiota help protect the body by competing with potential pathogens Various activities of the normal microbiota make it hard for pathogens to compete Secrete antimicrobial substances that limit pathogen growth Consumption of nutrients makes them unavailable to pathogens Create an environment unfavorable to other microorganisms by changing pH Helps stimulate the body’s second line of defense Promote overall health by providing vitamins to host |
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| Other First-Line Defenses |
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| Many body organs secrete chemicals with antimicrobial properties Lacrimal glands that bathe the eye Saliva Stomach acid |
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| Second Line of Defenses |
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| Operates when pathogens succeed in penetrating the skin or mucous membranes Nonspecific defense Composed of cells, antimicrobial chemicals, and processes but no physical barriers Many of these components are contained or originate in the blood |
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| Blood |
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| Operates when pathogens succeed in penetrating the skin or mucous membranes Nonspecific defense Composed of cells, antimicrobial chemicals, and processes but no physical barriers Many of these components are contained or originate in the blood |
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| Plasma vs Serum |
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| Formed Elements |
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| Erythrocytes- carry oxygen and carbon dioxide in the blood (4.2-6.2x109/ml) Platelets- involved in blood clotting and inflammation (1.3-4x108/ml) Leukocytes- involved in defending the body against invaders (4.5-11x106/ml) 2 groups: Granulocytes Agranulocytes |
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| Human Leukocytes |
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| Granulocytes: Neutrophils: 50-70% of circulating WBC Multi-lobed nucleus (>3 masses) >1010 neutrophils made every day Major phagocytes; Cells of acute inflammation Eosinophils: 1-3% of circulating WBC Bilobed nucleus; Parasite defense; Red granules Basophils: 0.5-1% of circulating WBC Bilobed nucleus; Contain histamine; Blue granules |
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| Agranulocytes |
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| Lymphocytes Monocytes |
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| Macrophages |
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| Phagocytic cells of the second line of defense Monocytes leave the blood (via diapedesis), enter tissue, and differentiate into macrophages. Some become fixed in a particular tissue, some remain free to wander and phagocytize throughout the body Fixed macrophages include microglial cells (central nervous system), mesangial cells (Kidney) and Kupffer cells (liver) All macrophages, plus monocytes attached to endothelial cells, constitute the mononuclear phagocytic system (formerly called the reticuloendothelial system (RES)) |
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| Lab Analysis of Leukocytes |
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| The differential white blood cell count test can signal signs of disease Increased eosinophils can indicate allergies or parasitic worm infection Bacterial diseases often show increase in leukocytes, mostly neutrophils Viral infections show increase in lymphocytes |
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| Second Line of Defense |
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| Phagocytosis Extracellular killing by leukocytes Nonspecific chemical defenses Inflammation Fever |
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| Phagocytosis |
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| Cells capable of phagocytosis (certain leukocytes or their derivatives) are called phagocytes Phagocytosis is performed chiefly by neutrophils (microphages) and macrophages. Can be divided into 5 stages |
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| Host Cell Protection |
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| The host’s cells are protected from destruction by the phagocytes Some phagocytes have receptors for bacterial surface components, such as flagellar proteins or cell wall components, that are lacking on the body’s cells Opsonins such as certain complement split products and antibody provide a handle for the phagocyte |
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| Extracellular Killing by Leukocytes |
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| Eosinophils Natural Killer Lymphocytes (NK cells) Neutrophils |
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| Nonspecific Chemical Defenses |
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| Lysozyme Complement Interferon Defensins Lactoferrin |
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| Complement System |
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| Set of serum proteins designated numerically according to the order of their discovery Complement activation results in lysis of the foreign cell Complement can be activated in several ways: Classical Pathway Alternate Pathway |
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| The Classical Pathway |
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| • Complement named for the events of this originally discovered pathway • Various complement proteins act nonspecifically to “complement” the action of antibodies |
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| The Alternate (Properdin) Pathway |
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| • Activation occurs independent of antibodies • Less efficient than the classical pathway • Useful in early stages of infection before antibodies have been made • Initiated by interaction between properdin factors B, D, and P and the endotoxins and LPS from bacteria and fungi • Stabilizes molecules of C3b that are normally in the blood in small quantities |
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| The Alternate (Properdin) Pathway |
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| • Stabilized C3b combines with the properdin factors to form an enzyme that cleaves C3 to produce more C3b • C3b combines with properdin B to form a different enzyme which cleaves C5 molecules • The complement cascade then continues as in the classical pathway |
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| TEM of a Cell Damaged by Complement Membrane Attack Complexes Interferons |
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| • Protein molecules released by host cells to nonspecifically inhibit the spread of viral infections • Particularly effective against viruses with RNA genomes • Cause many phys. symptoms typically associated with viral infections • 3 Classes – Alpha – Beta – Gamma |
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| Interferons |
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| • Alpha and beta interferons are present early in the infection • Gamma interferon appears later in the course of infection |
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| Interferon Therapy |
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| • It was thought that this might be a good antiviral treatment • Many viral infections don’t respond to interferon therapy at all • Only a slight effect is seen with those viral infections that do respond |
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| Defensins |
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| • Small peptides that function nonspecifically to protect against a broad range of pathogens • Act against pathogens in various ways – Punch holes in cytoplasmic membranes – Interfere with internal signaling and other metabolic processes – Interfere with the protein that preserves the shape of bacterial proteins under heat stress • In humans, inflammation increases the production of defensins |
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| Inflammation |
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| • Nonspecific response to tissue damage resulting from various causes • Characterized by redness (rubor), heat (calor), swelling (tumor), and pain (dolor) • Two types – Acute – Chronic |
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| Acute inflammation |
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| – Develops quickly and is short lived – Is usually beneficial – Important in the second line of defense • Dilation and increased permeability of the blood vessels • Migration of phagocytes • Tissue repair |
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| Chronic inflammation |
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| • Develops slowly and lasts a long time – Can cause damage to tissues |
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| Stimulation of Inflammation by C3a & C5a |
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| Cardinal Signs of Inflammation: ? Rubor = redness ? Calor = heat ? Tumor = edema ? Dolor = pain |
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| Chemical Mediators of Inflammation Fever |
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| • A body temperature over 37?C • Results when chemicals called pyrogens trigger the hypothalamus to increase the body’s core temperature • Various types of pyrogens – Bacterial endotoxins – Cytoplasmic contents of bacteria released by lysis – Antibody-antigen complexes – Interleukin-I (IL-1) |
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| Fever Production |
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| • IL-1 production causes the hypothalamus to secrete prostaglandin which resets the hypothalamic “thermostat” • Communication with the brain initiates muscle contractions, increased metabolic activity, and constriction of blood vessels which raises the body’s temperature • Chills associated with fever are due to the reduced blood flow of constricted vessels • Decrease in IL-1 production results in the body’s temperature returning to normal |
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| Benefits of Fever |
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| • Enhances the effects of interferons • Inhibits growth of some microorganisms • May enhance the performance of phagocytes, cells of specific immunity, and the process of tissue repair |
