Principles of Immunology

Antigens2/9/06

“It is only when you give of yourself that you truly give.”

K Gibran

Word List

Adjuvant Antigen Epitope Hapten Immunogen Xenogeneic

Antigens

Antigen-Antibody-generating substance

Antigen-A substance that will bind to antibody

Immunogen-A substance that will elicit an immune response

Antigenic Macromolecules

Antigens are generally proteins or polysaccharides.

Lipids are not generally immunogenic (or antigenic) unless they are complexed with proteins or polysaccharides

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

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

Properties of Immunogenicity

Chemical composition-Proteins; Primary, secondary, tertiary and quaternary structure all contribute. Haptens

Ability to be processed by APCs- Function of size

Biological Influences on Immunogenicity

Genotype of host-Expression of MHC genes

Dose of route of antigen presentation Immunological tolerance Vaccines Lymph or circulatory system

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

Epitopes

The active region of an immunogen (One antigen may have multiple epitopes)

Ag/Lymphocyte Interaction

Ag/Lymphocyte Interaction

Ag/T Lymphocyte Interaction

Ternary complex TCR MHC II molecule Antigen (peptide)

Also includes Co-receptor - CD4