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Antigen and Antigen Receptors

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Immunogen- Substance capable of generating a specific immune response and ... 1000-6000D May or May not be ... Continuous/Linear-Single polypeptide segment. ... – PowerPoint PPT presentation

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Title: Antigen and Antigen Receptors


1
Antigen and Antigen Receptors
  • Lecture 5

2
Immune Response is Antigen-Driven
3
Immunogen- Substance capable of generating a
specific immune response and binding to immune
components
  • Bacterial
  • O antigens of Salmonella
  • Flagellin
  • Toxins
  • Viral
  • Viral capsid proteins
  • Viral envelope glycoproteins

4
Antigen
  • Substance capable of binding specifically to
    immune components.

5
Haptens
  • Low mw molecules.
  • Antibiotics, drugs
  • Not immunogenic, unless...

HAPTENS
6
Haptens
  • Low mw molecules.
  • Not immunogenic, unless...
  • conjugated to high mw compounds (carriers) to
    gain immunogenicity

CARRIER
HAPTENS
7
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8
  • What affects Immunogenicity ?

9
Chemical Families
Immunogenic?
  • Proteins almost always
  • Carbohydrates potentially
  • glycoproteins usually
  • Lipids poorly
  • Nucleic Acids poorly

10
Requirements for Immunogenicity
  • High molecular weight
  • lt1000D-Not Immunogenic (penicillin)
  • 1000-6000D May or May not be immunogenic
    (insulin)
  • gt6000D-Generally immunogenic (albumin, Tetanus
    toxin)
  • Chemically complex
  • homopolymers not generally immunogenic
  • Ex Polylysine-30,000 D, Poly-D-Glutamic
    acid-50,000D
  • Degradable
  • Foreignness

11
Foreignness
Bovine albumin-specific Immature Lymphocyte
Response to Immunization
Bovine albumin
NO
Apoptosis
No Tetanus Toxoid Antigen
Yes
Toxoid-Specific Immature Lymphocyte
Mature Lymphocyte
12
Foreignness
Response to Immunization
NO
Cow
Bovine Albumin
Yes
Sheep
Chicken
Yes
13
Immunogenicity
  • Antigen
  • Dose
  • Low Zone Tolerance
  • High Zone Tolerance
  • Route of Admn.
  • SCgtIPgtIVgtIntragastric

14
Low-Zone and High-Zone Tolerance
15
Enhancing Immunogenicity
  • Administration of Protein in Adjuvants.
  • Incomplete Freunds adjuvant-oil-in- water
    emulsion
  • Complete Freunds adjuvant-oil-in-water emulsion
    plus dead Mycobacteria
  • Aluminum hydroxide gel

16
Adjuvants-Mode of Action
  • Delayed Release-Prolonged Antigen Persistence
  • Enhance Costimulatory Signals
  • Induce Granuloma formation
  • Stimulates Lymphocytes Nonspecifically

17
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18
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19
Antigen Receptors
  • Recognition of Antigen by Lymphocytes

20
Cell Surface Immunoglobulin
  • Antigen Receptor on B Cells

21
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22
B Cell Antigen Receptor Cell Surface
Immunoglobulin
23
B Cell Antigen Receptor
24
T Cell Receptor
  • Antigen Receptor on T Cells

25
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27
Antigen Recognition by Lymphocytes
28
B Cell Antigen Recognition
  • Via Surface Immunoglobulin
  • Recognize and bind FREE ANTIGEN IN SOLUTION
  • B Cells bind Native Protein Antigen

29
Antigen Recognition By B Lymphocytes
30
B Cell Antigen Recognition
31
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32
What do B cells recognize in the antigen?
  • Epitopes-Antigenic Determinant
  • Discrete Sites on the Macromolecule

33
B Cell Epitope
  • Portion of Ag that binds receptor
  • Antigenic determinant
  • 5-22 amino acids
  • Multideterminant Ags have many different
    epitopes on the same molecule

binding site
34
B Cell Epitope
  • Continuous/Linear-Single polypeptide segment.
  • Conformational/Discontinuous-Amino acids from
    different parts of the Sequence brought together
    by Protein folding.

binding site
35
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36
Binding of Antigens
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