1. Antigens Where we’re going- Immunogenicity vs antigenicity
What makes for a good immunogen
Haptens
Pattern recognition receptors

2. Aulanni’am Biochemistry Laboratory Faculty of Sciences_UB
Antigens
Aulanni’am
Biochemistry Laboratory
Faculty of Sciences_UB

3. Some definitions: Immunogenicity
Immunogen, for practical purposes= antigen
Antigenicity- ability to react with antibodies or Tcells;
all immunogens are antigens, but haptens have antigenicity but not immunogenicity.

4. Immunogen’s contribution- usually think “protein”
Foreignness-
Size- > 100 kDa better, < 10 kDa worse, especially for proteins
Complexity- homopolymers poor, heteropolymers better
Easily processed better than poorly processed; adding L-amino acids to a D-polymer increases its immunogenicity.

5. Genetics- mouse studies- responders and non-responder mice.
Dosage and route of administration- the pneumococcal polysaccharide story.
Route determines which lymph tissues meet the antigen- e.g., spleen vs local lymph nodes.

6. contribution- adjuvants
Something that stimulates the immune response to the antigen.
Alum- ppt’s, prolongs persistence
Inflammatory- dead Mycobacterium
Non-specific proliferation of cells- LPS,

7. Epitopes, or Ag determinants
Our cells don’t react to the whole molecule, but to parts- epitopes
B cells react to differently to epitopes than do T cells.
Remember- interaction is specific!

9. How B cells do it
An epitope can be non-sequential and can be brought together spatially, producing a single epitope.
B cell eptitopes tend to be on the surface,.

10. How T cells do it
The binding is ternary- three components- MHCII, TCR, antigen. Only parts are displayed.
No MHC binding= no antigenicity
B cell eptitopes tend to be on the surface, but T cells can be from the interior of the molecule.

11. Haptens Haptens aren’t immunogenic alone.
BUT- when bound to a carrier, Ab’s are produced that DO bind to the unbound hapten

12. Toll-like Receptors Recognize bacterial patterns. The response:
Attraction of phagocytic and Antigen-presenting cells- better at stimulating T cells
Activation of macrophages
Induction of interferon
Induces secretion of several cytokines

13. Summary… Terms: Immunogen(icity), antigen(icity), hapten
What makes a good antigen?
Adjuvants and what they might do
B-cell epitopes and T cell epitopes- differences and why
Haptens, and practical applications
Toll-like receptors- examples of what they recognize, types of response.