Antigens/Antibodies

Chapters 4-6

Antigen vs. Immunogen • Antigen

– Any substance that can bind to an antibody or T cell receptor

• Immunogen – Any substance that

can elicit an immune response

– All immunogens are antigens

– Not all antigens are immunogens, i.e. haptens

Immunogenicity of Antigens • Determined by

– Foreignness – Molecular Size – Chemical

Composition – Degradability

• Influenced by – Host genotype – Dose and route of

administration – Presence of

adjuvants

Epitopes • Discrete sites on immunogens recognized

by antibodies or T cell receptors • Macromolecules contain many epitopes with

different immunogenicities • Immunogenicity can vary between

individuals and populations. • Some epitopes are immunodominant

• Identification of B-cell epitopes within the HPV16 E7 protein.

• Overlapping peptides were generated and injected into mice.

• The antibody response to each peptide was measured by ELISA.

• Comerford, S.A. et al. J. Virol. 65:4681-4690, 1991

Epitopes • Overlapping • Non-overlapping

• Allosteric • Linear • Conformational • Neoantigen

Antibodies

Figure 4-7

Secreted vs. Membrane Forms

Antibody-Mediated Effector Functions

Antibody Mediated Effector Functions

• Opsonization – IgG

Antibody Mediated Effector Functions

• Opsonization – IgG

• Complement Activation IgM>IgG

• ADCC – IgG, IgE, IgA