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INNATE IMMUNITY – NONSPECIFIC DEFENSES OF THE HOST

CHAPTER 16. INNATE IMMUNITY – NONSPECIFIC DEFENSES OF THE HOST. The Concept of Immunity. Susceptibility : Lack of resistance to a disease Immunity : Ability to ward off disease Innate immunity : Defenses against any pathogen Adaptive immunity : Immunity, resistance to a specific pathogen.

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INNATE IMMUNITY – NONSPECIFIC DEFENSES OF THE HOST

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  1. CHAPTER 16 INNATE IMMUNITY – NONSPECIFIC DEFENSES OF THE HOST

  2. The Concept of Immunity • Susceptibility: Lack of resistance to a disease • Immunity: Ability to ward off disease • Innate immunity: Defenses against any pathogen • Adaptive immunity: Immunity, resistance to a specific pathogen

  3. The Concept of Immunity • Host Toll-like receptors (TLRs) attach to • Pathogen-associated molecular patterns (PAMPs) • TLRs induce cytokines that regulate the intensity and duration of immune responses

  4. Physical Factors • Skin • Epidermis consists of tightly packed cells with • Keratin, a protective protein Figure 16.2

  5. Physical Factors • Mucous membranes • Mucus: Traps microbes • Ciliary escalator: Microbes trapped in mucus are transported away from the lungs

  6. Ciliary Escalator Figure 24.7

  7. Ciliary Escalator Figure 16.4

  8. Physical Factors • Lacrimal apparatus: Washes eye • Saliva: Washes microbes off • Urine: Flows out • Vaginal secretions: Flow out

  9. Lacrimal Apparatus Figure 16.3

  10. Q&A During one year, nosocomial infections occurred in 74 patients in one hospital. All 74 patients were intubated and mechanically ventilated. The infections were caused by Burkholderia cepacia transmitted in nonsterile mouthwash.

  11. Q&A Why did these patients develop infections while others who used the mouthwash were not infected?

  12. Chemical Factors • Fungistatic fatty acid in sebum • Low pH (3–5) of skin • Lysozyme in perspiration, tears, saliva, and urine • Low pH (1.2–3.0) of gastric juice • Low pH (3–5) of vaginal secretions

  13. Normal Microbiota and Innate Immunity • Microbial antagonism/competitive exclusion: Normal microbiota compete with pathogens or alter the environment • Commensal microbiota: One organism (microbe) benefits and the other (host) is unharmed • May be opportunistic pathogens

  14. Formed Elements in Blood

  15. Formed Elements in Blood

  16. Formed Elements in Blood

  17. Differential White Cell Count • Percentage of each type of white cell in a sample of 100 white blood cells

  18. Components of Lymphatic System Figure 16.5a

  19. The Lymphatic System Figure 16.5b–c

  20. Phagocytosis • Phago: From Greek, meaning eat • Cyte: From Greek, meaning cell • Ingestion of microbes or particles by a cell, performed by phagocytes Phagocytic cells: Neutrophils, Fixed macrophages, Wandering macrophages Figure 16.6

  21. Phagocytosis Figure 16.7

  22. Microbial Evasion of Phagocytosis

  23. Inflammation • Acute-phase proteins activated (complement, cytokine, and kinins) • Vasodilation (histamine, kinins, prostaglandins, and leukotrienes) • Redness • Swelling (edema) • Pain • Heat

  24. Chemicals Released by Damaged Cells

  25. The Process of Inflammation Figure 16.8a, b

  26. Phagocyte Migration and Phagocytosis [Insert Animation Inflammation: Overview, Steps.] Figure 16.8c

  27. Tissue Repair Figure 16.8d

  28. Fever • Abnormally high body temperature • Hypothalamus normally set at 37°C • Gram-negative endotoxin cause phagocytes to release interleukin–1 (IL–1) • Hypothalamus releases prostaglandins that reset the hypothalamus to a high temperature • Body increases rate of metabolism and shivering which raise temperature • Vasodilation and sweating: Body temperature falls (crisis)

  29. Disadvantages Tachycardia Acidosis Dehydration 44–46°C fatal Fever • Advantages • Increases transferrins • Increases IL–1 activity • Produces Interferon

  30. The Complement System • Serum proteins activated in a cascade • Activated by • Antigen-antibody reaction • Proteins C3, B, D, P and a pathogen • C3b causes opsonization • C3a + C5a cause inflammation • C5b + C6 + C7 + C8 + C9 cause cell lysis

  31. The Complement System Figure 16.9

  32. Effects of Complement Activation • Opsonization or immune adherence: Enhanced phagocytosis • Membrane attack complex: Cytolysis • Attract phagocytes Figure 16.10

  33. Inflammation Stimulated by Complement Figure 16.11

  34. Classical Pathway of Complement Activation Figure 16.12

  35. Alternative Pathway of Complement Activation Figure 16.13

  36. Lectin Pathway of Complement Activation Figure 16.14

  37. Some Bacteria Evade Complement • Capsules prevent C activation • Surface lipid-carbohydrates prevent membrane attack complex (MAC) formation • Enzymatic digestion of C5a

  38. Interferons (IFNs) • IFN- and IFN-: Cause cells to produce antiviral proteins that inhibit viral replication • Gamma IFN: Causes neutrophils and macrophages to phagocytize bacteria

  39. Antiviral Actions of Interferons (IFNs) Figure 16.15

  40. Antimicrobial peptides Lyse bacterial cells Innate Immunity • Transferrins • Bind serum iron

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