Bio 328 Immunology

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Bio 328 Immunology Antigens
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• Antigens
• Immunogenicity vs. antigenicity
• Factors that influence immunogenicity
• Factors of the immunogen
• Factors of the biological system
• Adjuvants
• Epitopes
• B-cell epitopes
• T-cell epitopes
• Haptens
• Superantigen
• Mitogens

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B cell activation Competency signal (1) and (2)
and Proliferation signal (3)
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• Factors that influence immunogenicity
• Properties of the immunogen
• Foreignness
• Molecular size
• Chemical complexity
• Susceptibility to Ag processing
• Properties of the biological system
• Genotype of the recipient
• Dosage and route of administration
• Adjuvants

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Alum Al NH4 (SO4)2 . 12 H2O
(Crystals puncture lysosome and trigger formation
of the inflammasome)
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Muramyl-dipeptide
(Recognized by NLRs)
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B cell activation Competency signal (1) and (2)
and Proliferation signal (3)
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Karl Landsteiner (1868-1943) ABO blood group
system Rhesus factor Polio virus Haptens
specificity of Ag-Ab interactions 1930 Noble
Medicine
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• Epitopes
• Properties of B-cell epitopes.
• Size of the B-cell epitope
• Nature of the Ag-binding site of the antibody
• Hydrophilic groups on the protein surface
• Sequential or non-sequential amino acids
• Located in flexible regions
• Multiple, overlapping B-cell epitopes

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Inhibition of dextran-anti-dextran interaction by
glucose oligomers.
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Antigen the octapeptide Angiotensin II
Antibody (Fab)
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Protruding glutamine
Hen egg lysozyme (green/red) recognized by the
anti-HEL antibody (L chain yellow, H chain blue).
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Sperm whale myoglobin five sequential epitopes.
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Non-sequential epitope of lysozyme Red contact
with LC Blue contact HC White contact with LC
and HC
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• Epitopes
• Properties of T-cell epitopes.
• T-cell epitopes are protein fragments
• T-cell epitopes are presented by MHC molecules
• The MHC molecule can present various oligomeric
  epitopes
• T-cell epitopes are often internal
• T-cell epitopes are always sequential
• The dominance of T-cell epitopes is determined in
  part by the set of MHC molecules expressed by the
  individual

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B cell epitope
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Immunogenicity depends on MHC binding.
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The End