1. Principles of Immunology Antigens 2/9/06 “It is only when you give of yourself that you truly give.” K Gibran

2. Word List  Adjuvant  Antigen  Epitope  Hapten  Immunogen  Xenogeneic

3. Antigens  Antigen-Antibody-generating substance  Antigen-A substance that will bind to antibody  Immunogen-A substance that will elicit an immune response

4. Antigenic Macromolecules  Antigens are generally proteins or polysaccharides.  Lipids are not generally immunogenic (or antigenic) unless they are complexed with proteins or polysaccharides

5. Types of Antigens  Autoantigens-”self”  Alloantigens-”same species”  Heteroantigens-”different species”  T-cell dependent antigens-Requires T cell involvement; proteins  T-cell independent antigens-Does not require T cell involvement; polysaccharides

6. Properties of Immunogenicity  Degree of “foreignness”-Based on genetic relatedness  Molecular Size-Usually MW >100,000; <10,000 non immunogenic; 10,000- 100,000 MW is imunogenetically variable

7. Properties of Immunogenicity  Chemical composition-Proteins; Primary, secondary, tertiary and quaternary structure all contribute. Haptens  Ability to be processed by APCs- Function of size

8. Biological Influences on Immunogenicity  Genotype of host-Expression of MHC genes  Dose of route of antigen presentation Immunological tolerance Vaccines Lymph or circulatory system

9. Biological Influences on Immunogenicity  Adjuvants-Enhance immunogenicity Potential mechanism  Ag persistence  Cell signaling or cytokine effect  Induction of inflammation  Lymphocyte stimulation Types  Alum  Freund’s incomplete adjuvant  Freund’s complete adjuvant

11. Epitopes  The active region of an immunogen (One antigen may have multiple epitopes)

12. Ag/Lymphocyte Interaction

14. Ag/T Lymphocyte Interaction  Ternary complex TCR MHC II molecule Antigen (peptide) Also includes Co-receptor - CD4