Immunology I - 1

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Author:
ed70
ID:
36006
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Immunology I - 1
Updated:
2010-09-20 11:04:06
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Immunology
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Immune Defense
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  1. What is the Immune System:
    A collection of molecules, cells, tissues and organs whose primary funciton is defense
  2. Exceptions to the Primary Defensive Role:
    • Exaggerated specific responses to non-pathogenic environmental antigens (allergy)
    • Any exaggerated specific responses that are tissue damaging (hypersensitivities)
    • Specific, exaggerated and destructive responses to self-antigens (autoimmunities)
    • Variable responses to self, neoantigens - (cancers)
    • Strong barriers to organ and tissue transplantation (allogenic responses)
  3. Bodies Barriers:
    All surfaces exposed to the "outside world" provide barriers to penetration and infection
  4. Infection and Inflammation: Sequence of Events in a nonspecific Local Inflammatory Response to Bacteria (6 steps)
    • 1. Entry of bacteria into tissue; injury to tissues causes release of chemicals to initiate the following events
    • 2. Vasodilation of the microcirculation in the infected area, leading to increased blood flow
    • 3. Large increase in protein permeability of the capillaries and venules in the infected area, with resulting diffusion of protein and filtration of fluid into the interstitial fluid
    • 4. Chemotaxis: movement of leukocytes from the venules into the interstitial fluid of the infected area
    • 5. Destruction of bacteria in the tissue either through phagocytosis or by other mechanisms
    • 6. Tissue repair
  5. Inflammation: General Properties:
    Initiators and purpose
    • - The body's defense mechanisms in response to tissue damage and/or infection
    • Initiators - infection, trauma (physical or chemical), and pathologic immune responses
    • Purpose - identify the area affected and call into play mechanisms that lead to: elimation of the inflammatory stimulus and healing
  6. Two Defense Against Infection
    • 1. Innate, non-specific defenses
    • 2. Acquired, adaptive, specific defenses
  7. Innate, non-specific defenses:
    • -Physical and/or chemical barriers; i.e. epithelia
    • -Molecular - complement, cytokines, chemokines, acute phase proteins
    • -Cellular - phagocytic cells, natural killer (NK) cells
  8. Acquired, adaptive, specific defenses
    • -Molecular - antibodies
    • -Cellular - lymphocytes: naive, effector, and memory lymphocytes
  9. The Response by both innate and specific defense systems to Infection consist of 2 Phases:
    • 1. Recognition - of a potential pathogen and/or its products by host cells and molecules
    • 2. Recruitment and/or generation of destructive effector mechanisms - to contain or eliminate the potential pathogen and/or its products
  10. The First Time an Individual Encouters a Pathogen (4)
    • Immediate - Innate - Physical and chemical barriers
    • 0-4 hours - Innate - Molecular and cellular recognition and response
    • 4-96 hours - Innate - molecular and cellular recruitment of cells from circulation and their activation
    • 4-14 days - Acquired, specific - dendritic cells, macrophage and lymphocytes
  11. Neutrophils
    • The classic phagocytic cell
    • (50-70% of all blood leukocytes)
  12. Monocytes
    The precursors to all tissue macrophage (1-6% of all blood luekocytes)

    • Released from bone marrow and circulate in blood.
    • When they leave blood and migrate into different tissues, the differentiate into macrophage (highly phagocytic cells) characteristic of that tissue
  13. Macrophage
    • The tissue - specific, fully differentiated, highly phagocytic descendents of blood monocytes.
    • When partly activated, these cells can also be antigen-processing and presenting cells
  14. Dendritic Cells
    Antigen processing and presenting cells

    <<1% of all blood leukocytes
  15. Most Important Cells Involved in Innate Immune Recognition: (3)
    • Dendritic Cells - are capable of recgonizing and responding to smaller pathogens and their molecular products, ex viruses
    • Neutrophils and macrophage - capable of recognizing and responding to larger pathogens and pathogenic materials, for example, intact bacteria.
    • Natural Killer (NK) Cells = capable of recognizing and responding to virally-infected host cells by killing them.
  16. Characteristics of Innate Immune Defense Recognition:
    • -A limited number of binding specificities (distinct receptors) are expressed by cells of the innate defense system
    • -Recognition and response are rapid - measured in minutes to hours
    • -There is no specific memory generated as a consequence of recognition and response
  17. The Major Functions of Cell-Surface Pattern Recognition Receptors
    • -Direct uptake of pathogens by phagocytes and dendritic cells.
    • - Macrophage mannose receptors
    • - Macrophage scavenger receptors
    • -Triggering signaling pathways (example: toll-like receptor (TLR) signaling) stimulates production of anti-microbial peptides and inflammatory cytokines
  18. Innate Cellular Immunity to Infection
  19. Tissue macrophage (and dendritic cells) are the sentinel cells
    • –Macrophage attempt to phagocytose and kill the microbe intracellularly
    • –Macrophage secrete cytokines and chemokines in response
    • –The endothelial cells of blood vessels adjacent to the site are “activated”
    • –Inflammatory cells, like neutrophils, are recruited to the site
  20. Innate Cellular Effector Mechanisms
    • •Phagocytic cells like neutrophils, which have been attracted to sites of inflammation and both resident tissue macrophage and additional recruited monocytes/macrophage are capable of very fast action
    • •Phagocytic activity may often be sufficient to clear the pathogen
    • •If the infection is not completely cleared, these cells can contain the infection until the specific defenses can be mobilized

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