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Understanding Antigens and Immunogenicity in Immunology Lessons

Join Dr. Jennifer Nyland to explore immunogens, antigens, haptens, and factors influencing immunogenicity. Learn about antigen structures, superantigens, and immune responses. Enhance your vocabulary and comprehension of the immune system.

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Understanding Antigens and Immunogenicity in Immunology Lessons

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  1. Antigens Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586 Email: jnyland@uscmed.sc.edu

  2. 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

  3. Overview of the immune system

  4. Vocabulary • Immunogen • Antigen (Ag) • Hapten • Epitope or antigenic determinant • Antibody (Ab)

  5. Factors influencing immunogenicity

  6. Immunogenicity: contribution of immunogen • Foreignness • Size • Chemical composition • Primary structure --- sequence determinants • Secondary structure • Tertiary structure • Quarternary structure Conformational determinants

  7. Immunogenicity: contribution of immunogen • Foreigness • Size • Chemical composition • Physical form • Particular > Soluble • Denature > Native

  8. Immunogenicity: contribution of immunogen • Foreigness • Size • Chemical composition • Physical form • Degradability • Ag processing by Ag-presenting cells (APC)

  9. Immunogenicity: contribution of biological system • Genetics • Species • Individual • Responders vs Non-responders • Age

  10. Immunogenicity: method of administration • Dose • Route • Subcutaneous > Intravenous > Intragastric • Adjuvant • Substances that enhance immune response to Ag

  11. 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

  12. 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

  13. Antigens: T-dependent • Require T help to activate B cells • Proteins • Structure • Examples • Microbial proteins • Non-self or altered-self proteins

  14. Hapten-carrier conjugates • Definition • Ag only if bound to carrier protein • Structure • Native determinants • Haptenic determinants

  15. Antigenic determinants recognized byB cells and Ab • Composition • Proteins, polysaccharides, nucleic acids, haptens • Sequence (linear) determinants • Conformational determinants • Size • 4-8 residues

  16. Antigenic determinants recongized byB cells and Ab • Composition • Size • Number • Limited (immunodominantepitopes) • Located on the external surface of the Ag (exposed)

  17. 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

  18. Superantigens Ag T cell T cell • Definition • Polyclonal T cell response • Examples • Staphlycoccalenterotoxins • Toxic shock toxin TCR TCR SuperAg MHC MHC APC APC

  19. 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

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