Microbiology

1. Microbiology Chapter 14 Host Defenses � Overview and Innate

2. 2 14.1 Defense Mechanisms of the Host Host Defenses Innate, natural defenses: present at birth, provide nonspecific resistance to infection Adaptive immunities: specific, must be acquired

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4. 4 14.1 Defense Mechanisms of the Host First line of defense � any barrier that blocks invasion at the portal of entry � nonspecific Second line of defense � protective cells and fluids; inflammation and phagocytosis � nonspecific Third line of defense � B&T Lymphocytes & Antibodies � specific

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6. Innate and Adaptive Defenses

7. 7 Physical or Anatomical Barriers: First Line of Defense Skin and mucous membranes of respiratory, urogenital, eyes, and digestive tracts Outermost layer of skin is composed of epithelial cells compacted, cemented together, and impregnated with keratin; few pathogens can penetrate if intact Flushing effect of sweat glands Damaged cells are rapidly replaced Mucous coat impedes attachment and entry of bacteria Blinking and tear production Stomach acid Nasal hair traps larger particles

8. Factors in Protection from Skin Layers � Stratified Keratinized � (Dry �tough)

9. Respiratory Tract Mucosae Cilia sweep dust- and bacteria-laden mucus away from lower respiratory passages

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12. 12 Chemical Defenses Sebaceous secretions Lysozyme, an enzyme that hydrolyzes the cell wall of bacteria, in tears High lactic acid and electrolyte concentration in sweat Skin�s acidic pH Hydrochloric acid in stomach Digestive juices and bile of intestines Semen contains an antimicrobial chemical Vagina has acidic pH

13. Lysozyme

14. 14 Genetic Defenses Some hosts are genetically immune to the diseases of other hosts Some pathogens have great specificity Some genetic differences exist in susceptibility

15. 15 A healthy immune system is responsible for Surveillance of the body Recognition of foreign material Destruction of entities deemed to be foreign

16. 16 14.2 Structure and Function of the Organs of Defense and Immunity The study of the body�s second and third lines of defense is called immunology Functions of a healthy functioning immune system: Surveillance of the body Recognition of foreign material Destruction of entities deemed to be foreign

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18. 18 Immune System Large, complex, and diffuse network of cells and fluids that penetrate into every organ and tissue Four major subdivisions of immune system are: Reticuloendothelial system (RES) Extracellular fluid (ECF) Bloodstream Lymphatic system

19. 19 Immune System Definitions White blood cells (leukocytes) � innate capacity to recognize and differentiate any foreign material Nonself � foreign material Self � normal cells of the body Pathogen-associated patterns (PAMPs) � molecules shared by microorganisms Pathogen recognition receptors (PRRs) � receptors on WBCs for PAMPs

20. 20 Body Compartments that Participate in the Immune System The reticuloendothelial system The spaces surrounding tissue cells that contain extracellular fluid The bloodstream The lymphatic system

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22. 22 Reticuloendothelial System (RES) Network of connective tissue fibers that interconnects other cells and meshes with the connective tissue network surrounding organs Inhabited by phagocytic cells � mononuclear phagocyte system � macrophages ready to attack and ingest microbes that passed the first line of defense

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24. 24 Origin, Composition, and Functions of the Blood Whole blood consists of plasma and formed elements (blood cells) Serum is the liquid portion of the blood after a clot has formed � minus clotting factors Plasma � 92% water, metabolic proteins, globulins, clotting factors, hormones, and all other chemicals and gases to support normal physiological functions

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26. 26 A Survey of Blood Cells Hemopoiesis � production of blood cells Stem cells � undifferentiated cells, precursor of new blood cells Leukocytes � White blood cells Granulocytes: lobed nucleus Agranulocytes: unlobed, rounded nucleus

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28. 28 Granulocytes Neutrophils � 55-90% - lobed nuclei with lavender granules; phagocytes Eosinophils � 1-3% - orange granules and bilobed nucleus; destroy eukaryotic pathogens Basophils � 0.5% - constricted nuclei, dark blue granules; release potent chemical mediators Mast cells: nonmotile elements bound to connective tissue

29. Phagocytes Macrophages are the chief phagocytic cells Free macrophages wander throughout a region in search of cellular debris Kupffer cells (liver) and microglia (brain) are fixed macrophages

30. 30 Agranulocytes Lymphocytes � 20-35%, specific immune response B (humoral immunity) Activated B cells produce antibodies T cells (cell-mediated immunity) Activated T cells modulate immune functions and kill foreign cells Monocytes, macrophages � 3-7% - largest of WBCs, kidney-shaped nucleus; phagocytic Macrophages: final differentiation of monocytes Dendritic cells: trap pathogens and participate in immune reactions

31. 31 Erythrocytes and Platelet Lines Erythrocytes: develop from bone marrow stem cells, lose nucleus, simple biconcave sacs of hemoglobin Platelets: formed elements in circulating blood that are not whole cells

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33. 33 Lymphatic System Provides an auxiliary route for return of extracellular fluid to the circulatory system Acts as a drain-off system for the inflammatory response Renders surveillance, recognition, and protection against foreign material

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35. 35 Lymphatic Fluid Lymph is a plasma-like liquid carried by lymphatic circulation Formed when blood components move out of blood vessels into extracellular spaces Made up of water, dissolved salts, 2-5% proteins Transports white blood cells, fats, cellular debris, and infectious agents

36. 36 Lymphatic Vessels Lymphatic capillaries permeate all parts of the body except the CNS, bone, placenta, and thymus Thin walls easily permeated by extracellular fluid which is then moved through contraction of skeletal muscles Functions to return lymph to circulation; flow is one-direction � toward the heart � eventually returning to blood stream

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38. 38 Lymphoid Organs and Tissues Classified as primary and secondary Primary lymphoid organs � sites of lymphocytic origin and maturation � thymus and bone marrow Secondary lymphoid organs and tissues � circulatory-based locations such as spleen and lymph nodes; collections of cells distributed throughout body tissues � skin and mucous membranes � SALT, GALT, MALT

39. 39 Lymphoid Organs Thymus � high rate of growth and activity until puberty, then begins to shrink; site of T-cell maturation Lymph nodes � small, encapsulated, bean-shaped organs stationed along lymphatic channels and large blood vessels of the thoracic and abdominal cavities Spleen � structurally similar to lymph node; filters circulating blood to remove worn out RBCs and pathogens Miscellaneous � GALT, Peyer�s patch

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41. 41 14.3 Actions of the Second Line of Defense Recognition Inflammation Phagocytosis Interferon Complement

42. 42 Recognition Protein receptors within cell membrane of macrophages, called Toll-like receptors Detect foreign molecules and signal the macrophage to produce chemicals which: Stimulate an inflammatory response (nonspecific) Promote the activity of B and T cells (specific)

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44. 44 Inflammatory Response Classic signs and symptoms characterized by: Redness � increased circulation and vasodilation in injured tissues in response to chemical mediators and cytokines Warmth � heat given off by the increased blood flow Swelling � increased fluid escaping into the tissue as blood vessels dilate � edema; WBC�s, microbes, debris, and fluid collect to form pus; helping prevent spread of infection Pain � stimulation of nerve endings Possible loss of function

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48. 48 Unique Characteristics of Leukocytes Diapedesis � migration of cells out of blood vessels into the tissues Chemotaxis � migration in response to specific chemicals at the site of injury or infection

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50. 50 Fever Initiated by circulating pyrogens which reset the hypothalamus to increase body temperature; signals muscles to increase heat production and vasoconstriction Exogenous pyrogens � products of infectious agents Endogenous pyrogens � liberated by monocytes, neutrophils, and macrophages during phagocytosis; interleukin-1 (IL-1) and tumor necrosis factor (TNF) Benefits of fever: Inhibits multiplication of temperature-sensitive microorganisms Impedes nutrition of bacteria by reducing the available iron Increases metabolism and stimulates immune reactions and protective physiological processes

51. 51 Phagocytosis General activities of phagocytes: To survey tissue compartments and discover microbes, particulate matter, and dead or injured cells To ingest and eliminate these materials To extract immunogenic information from foreign matter

52. Phagocytosis Video Clip 52

53. 53 Phagocytes and Phagocytosis Main types of phagocytes: Neutrophils � general-purpose; react early to bacteria and other foreign materials, and to damaged tissue Eosinophils � attracted to sites of parasitic infections and antigen-antibody reactions Macrophages � derived from monocytes; scavenge and process foreign substances to prepare them for reactions with B and T lymphocytes

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56. 56 Mechanisms of Phagocytic Recognition, Engulfment, and Killing Chemotaxis and ingestion: phagocytes migrate and recognize PAMPs Phagosome Phagolysosome: lysosome fused with phagosome (death ~30 minutes) Destruction and elimination Oxygen-dependent system (respiratory burst) Liberation of lactic acid, lysozyme, and nitric oxide

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58. 58 Interferon Small protein produced by certain white blood cells and tissue cells Interferon alpha � lymphocytes and macrophages Interferon beta � fibroblasts and epithelial cells Interferon gamma � T cells Produced in response to viruses, RNA, immune products, and various antigens Bind to cell surfaces and induce expression of antiviral proteins Inhibit expression of cancer genes

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60. Interferon Video Clip 60

61. 61 Complement Consists of 26-30 blood proteins that work in concert to destroy bacteria and viruses Complement proteins are activated by cleavage (cascade reaction) Pathways Classical � activated by the presence of antibody bound to microorganism Alternative � Complement acts, independent of antibodies

62. 62 Stages in the Complement Cascade Initiation Amplification and cascade Polymerization Membrane attack

63. Complement Video Clip 63

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