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Antigens

Antigens. Where we’re going- Immunogenicity vs antigenicity What makes for a good immunogen Haptens Pattern recognition receptors. Antigens. Aulanni’am Biochemistry Laboratory Faculty of Sciences_UB. Some definitions:. Immunogenicity Immunogen, for practical purposes= antigen

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Antigens

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

  2. 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!

  8. How B cells do it An epitope can be non-sequential- 56-62 and 15-21 can be brought together spatially, producing a single epitope. B cell eptitopes tend to be on the surface,.

  9. 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.

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

  11. 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

  12. 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.

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