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Antigens. Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586 Email: jnyland@uscmed.sc.edu. Teaching objectives. To compare and contrast immunogen , antigen & hapten To describe the factors influencing immunogenicity To define the chemical nature of immunogens

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antigens

Antigens

Jennifer Nyland, PhD

Office: Bldg#1, Room B10

Phone: 733-1586

Email: jnyland@uscmed.sc.edu

teaching objectives
Teaching objectives
  • To compare and contrast immunogen, antigen & hapten
  • To describe the factors influencing immunogenicity
  • To define the chemical nature of immunogens
  • To compare the structures of T-independent and T-dependent antigens
  • To introduce the concept of hapten-carrier conjugates and their structure
  • To characterize antigenic determinants
  • To define superantigens
vocabulary
Vocabulary
  • Immunogen
  • Antigen (Ag)
  • Hapten
  • Epitope or antigenic determinant
  • Antibody (Ab)
immunogenicity contribution of immunogen
Immunogenicity: contribution of immunogen
  • Foreignness
  • Size
  • Chemical composition
    • Primary structure --- sequence determinants
    • Secondary structure
    • Tertiary structure
    • Quarternary structure

Conformational

determinants

immunogenicity contribution of immunogen1
Immunogenicity: contribution of immunogen
  • Foreigness
  • Size
  • Chemical composition
  • Physical form
    • Particular > Soluble
    • Denature > Native
immunogenicity contribution of immunogen2
Immunogenicity: contribution of immunogen
  • Foreigness
  • Size
  • Chemical composition
  • Physical form
  • Degradability
    • Ag processing by Ag-presenting cells (APC)
immunogenicity contribution of biological system
Immunogenicity: contribution of biological system
  • Genetics
    • Species
    • Individual
      • Responders vs Non-responders
  • Age
immunogenicity method of administration
Immunogenicity: method of administration
  • Dose
  • Route
    • Subcutaneous > Intravenous > Intragastric
  • Adjuvant
    • Substances that enhance immune response to Ag
chemical nature of immunogen
Chemical nature of immunogen
  • Proteins
  • Polysaccharides
  • Nucleic acids
  • Lipids
    • Some glycolipids and phospholipids can be immunogenic for T cells and illicit a cell-mediated immune response
antigens t independent
Antigens: T-independent
  • Activate B cells without MHC class II T help
  • Polysaccharides
  • Properties
    • Polymeric structure
    • Polyclonal B cell activation, but poor memory
    • Resistance to degradation
  • Examples
    • Pneumococcal polysaccharide, LPS
    • Flagella
antigens t dependent
Antigens: T-dependent
  • Require T help to activate B cells
  • Proteins
  • Structure
  • Examples
    • Microbial proteins
    • Non-self or altered-self proteins
hapten carrier conjugates
Hapten-carrier conjugates
  • Definition
    • Ag only if bound to carrier protein
  • Structure
    • Native determinants
    • Haptenic determinants
antigenic determinants recognized by b cells and ab
Antigenic determinants recognized byB cells and Ab
  • Composition
    • Proteins, polysaccharides, nucleic acids, haptens
    • Sequence (linear) determinants
    • Conformational determinants
  • Size
    • 4-8 residues
antigenic determinants recongized by b cells and ab
Antigenic determinants recongized byB cells and Ab
  • Composition
  • Size
  • Number
    • Limited (immunodominantepitopes)
    • Located on the external surface of the Ag (exposed)
antigenic determinants recognized by t cells
Antigenic determinants recognized byT cells
  • Composition
    • Proteins (some lipids)
    • Sequence determinants
      • Processed
      • MHC presentation (lipid presentation by MHC-like CD1)
  • Size
    • 8-15 residues
  • Number
    • Limited to those that can bind MHC
superantigens
Superantigens

Ag

T cell

T cell

  • Definition
    • Polyclonal T cell response
  • Examples
    • Staphlycoccal enterotoxins
    • Toxic shock toxin

TCR

TCR

SuperAg

MHC

MHC

APC

APC

summary of immune response
Summary of immune response
  • Adaptive immune response
    • Discrete determinants
    • Reacts with specific pathogen
  • Innate immune response
    • Broad molecular patterns
    • Reacts with a variety of pathogens