Immuno-04

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minderly
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85003
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Immuno-04
Updated:
2011-05-11 15:30:20
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Immunology MS1
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Immunology Lecture 4 Syllabus complete
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  1. immunogen vs. antigens
    • immunogen: substance cabable of inducing an immune response
    • antigen: substance capable of reacting with the antibodies produced by an immune response
    • all immunogens are antigens, but not all antigens are capable of eliciting their production
  2. heptens and carriers
    • heptens: synthetic compounds coupled to the protein
    • carriers: extracted proteins capable of serving as an immunogen to elicit antibodies to the hapten
  3. 2 categories of protein epitopes
    • linear/sequential
    • conformational/nonsequential
  4. 3 conclusions from sperm whale myoglobin antigen experiment
    • size of antigenic determinant is 6 aa
    • antibody response involves many antibodies recognizing numerous epitopes on a microbe/antigen
    • epitopes are located on outer surface of molecules in native configuration
  5. immunogenicity
    • strenght as an immunogen
    • ex. autologous bone marrow transplant
  6. Define autoantigen
    a self antigen (autologous)
  7. Define alloantigen
    • antigenic difference within a species
    • ex. blood transfusion
  8. Define xenoantigen
    • antigenic difference between species
    • ex. use horse anti-snake venom to treat human snake poisoning
  9. passive immunization
    • using xenoantigens to avoid dangers of an molecule (such as horse anti-snake serum for snake venom)
    • the person will elicit immune response against foreign proteins in hourse antiserum
  10. 6 factors affecting immunogenicity
    • foreignness: phylogenetic distance correlates with strength of immune response
    • molecular weight: >6000Da are good immunogens
    • chemical complexity: complex aa sequence is more immunogenic
    • enzymatically degradable: if degraded before it's processed by APC, it will fail to stimulate T cell
    • immunological status of host: most responsive in healthy young adults
    • dose and route
  11. 4 dose and route effects on immunogenicity
    • doses that are too high/low are not immunogenic
    • aggregated molecules are more immunogenic
    • IV and SC (subcutaneous) are less effective than IM (intramuscular) or ID (intradermal) routes
    • oral antigens can tolerize (turn off immune response)
  12. 4 Types of immunogens
    • polysaccharides
    • lipids
    • nucleic acids
    • proteins
  13. immunogenic properties of polysaccharides
    • glycoproteins & glycolipids are sometimes immunogenic
    • activates B1 cells only
  14. immunogenic properties of lipids
    poor immunogens unless they're attached to polysaccharides (glycolipid)
  15. immunogenic properties of nucleic acids
    poor antigens unless conjugated to protein carriers
  16. immunogenic properties of proteins
    • all foreign proteins are immunogenic
    • includes multi-epitope antigens
    • have B epitopes and T epitopes
  17. 4 types of antigen-antibody interactions
    • homologous: antigen is identical to immunogen
    • heterologous: cross reactivity (ex. anti-goat reacting with sheep serum)
    • native vs. modified: chemically modified self protein is recognized (ex. autoimmunity and hypersensitivity)
    • heterophile antigens: cross reaction with very different molecules that share an epitope
  18. What are adjuvants?
    additives that make immunogens more immunogenic
  19. 4 common mechanisms of action of adjuvants?
    • enhanced uptake of antigen by APC
    • delayed release of antigen by APC
    • induction of co-stimulatory molecule on APC
    • delivery of antigen by cytosol allowing induction of cytotoxic T-cell response
  20. 4 common mechanisms of action of adjuvants?
    • enhanced uptake of antigen by APC
    • delayed release of antigen by APC
    • induction of co-stimulatory molecule on APC
    • delivery of antigen by cytosol allowing induction of cytotoxic T-cell response
  21. B cells vs. T cells
    1. antigen interaction
    2. nature of antigen
    3. binding of soluble antigens?
    4. epitopes recognized
    • B cells:
    • 1. BCR binds Ag
    • 2. protein+polysaccharide+lipid antigens
    • 3. binds soluble antigens
    • 4. epitopes are accessible, sequential or nonsequential

    • T cells:
    • 1. TCR binds antigenic peptides bound to MHC
    • 2. peptide antigens
    • 3. binds soluble antigens only after processing into peptides by DC
    • 4. internal or exposed linear peptides produced by antigen processing (proteolytic degradation)
  22. Tempo of immune response
    • 1' response: 7-10d post exposure to immunogen, antibodies detectable in blood, transient
    • after pathogen elimination T and B cells differentiate into memory cells
    • 2' response: second exposure of same immunogen leads to rapid production of more antibodies due to activation of memory T and B cells

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