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Innate Immunity: The Immediate Response

This article discusses the benefits of a two-tiered immune system, the different groups of pathogens, and the two phases of the innate immune response. It also explores the role of epithelial barriers, complement activation, and the recognition of pathogens by phagocytes.

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Innate Immunity: The Immediate Response

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  1. Innate Immunity: The Immediate Response April 6, 2009 10:00-11:00

  2. Figure 8-1 BENEFITS OF A TWO-TIERED IMMUNE SYSTEM Innate Immunity is a pre-requisite for adaptive immunity

  3. Pathogens can be divided into 4 groups

  4. PATHOGENS ENTER VIA SEVERAL ROUTES

  5. LOCATION, LOCATION……. The site(s) at which a pathogen enters and resides direct the immune response

  6. Immediate Response Induced Response TWO PHASES OF INNATE IMMUNE RESPONSE Cells and proteins involved reside at sites of pathogen entry Proteins produced during the immediate response recruit help. Cells do not reside at the site, but rather respond to the cry for assistance

  7. THE FIRST STEPS IN INFECTION The pathogen must breech an epithelial surface, interior or exterior In order to be successful, the micro-organism must establish an initial focus or colony.

  8. Figure 8-6 EPITHELIUM IS AN ACTIVE BARRIER

  9. Figure 8-7 RESIDENT MICROFLORA PROTECT AGAINST PATHOGENS

  10. COMPLEMENT IS ACTIVATED BY PATHOGENS THAT BREECH THE EPITHELIUM

  11. Figure 8-9 ACTIVATION OF COMPLEMENT VIA THE ALTERNATIVE PATHWAY Functional C3b on the microbial surface bind factors B and D As a result…more C3b is generated as well as C3a C3b acts on macrophages C3a acts on endothelial cells

  12. COMPLEMENT PROMOTES VASCULAR PERMEABILITY

  13. Figure 8-10 FATE OF C3b DEPENDS ON THE CELL SURFACE

  14. Figure 8-11 HOST PROTEINS BLOCK ACTION OF MICROBIAL PROTEASES Serpins a-Macroglobulin

  15. INNATE IMMUNE EFFECTOR CELLS Short lived and not present in healthy tissue Long lived macrophages are always present in tissue Function: kill virally infected targets Functions: phagocytosis, secretion of enzymes and cytokines, antigen presentation Functions: phagocytosis cytokine production First cellular defenders

  16. RECOGNITION OF PATHOGENS Danger: Pathogens cause tissue damage thereby alerting the immune system Stranger: Pathogens have distinguishing membrane “patterns”, a.k.a. PAMPs Innate immune cells have receptors that recognize the patterns

  17. PHAGOCYTE PATHOGEN RECOGNITION RECEPTORS Complement Receptors: CR3 a.k.a. Cd11 and CR4 Pattern Recognition Receptors LPS, mannose, glycan, scavenger receptors recognize bacterial carbs. PAMP stimulate phagocytosis

  18. THE ACTIVATED MACROPHAGE INGESTS PATHOGENS 1. Recognition 2. Engulfment 3. Phagosome forms • Phagosome fuses • with lysozome • Acidification of • phagolysozome • Release of toxic • substances

  19. * ANTIMICROBIAL PRODUCTS OF PHAGOCYTES *NADPH oxidase in lysozomes generate toxic oxygen species in the RESPIRATORY BURST Chronic Granulomatous Disease: absence of NADPH; recurrent infections

  20. Figure 8-13 TOLL RECEPTORS ARE INVOLVED IN PATHOGEN RECOGNITION

  21. TOLL RECEPTOR RECOGNITION IS INDIRECT TLR-4 DOES NOT DIRECTLY BIND LPS

  22. Figure 8-14 TOLL RECEPTORS ACTIVATE A SIGNAL TRANSDUCTION CASCADE

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