Antigens
Terms
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- Immunogens
- substances that are usually foreign; capable of inducing a specific immune response.
- antigen
- any substance that binds specifically to an Ab or a Tcell receptor
- Example of an Ag that is not immunogenic
- Penicillin - a hapten that needs a carrier
- what 2 properties determine the recognition of a Ab or TcR for an antigen?
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-Conformation
-Chemical properties - 4 properties of a good immunogen/Ag:
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-Foreignness
-Chemical composition and heterogeneity
-Large/insoluble Ags for better Processing and presentation.
-Molecular size
-100kDa is good; 5 kDa is bad. - What is a hapten?
- a small antigenic molecule that is not immunogenic; to make immunogenic must be coupled with a carrier protein.
- adjuvant
- substances that enhance the immunogenicity of an antigen
- Are B-cell epitopes sequential or non?
- Either - can be contiguous amino acid residues, or noncontinuous, brought together by folding of the protein.
- What is a major determinant of whehter antibody will bind an antigen or not?
- Complementarity of fit.
- What types of residues on ?Antigens do Bcell antibodies recognize?
- Hydrophilic
- What could be a consequence of denaturing an antigen with Bcell epitopes?
- If non-sequential, will destroy the epitopes. These are only epitopes when undenatured.
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Are Tcell and Bcell epitopes
External or Internal? -
Tcell = internal; hydrophobic
Bcell = external; hydrophilic - What happens to Tcell epitopes on denatured proteins?
- Nothing; they're degraded to present on MHC2 anyway
- What determines whether an epitope can be a Tcell epitope or not?
- If it can bind to both the TCR AND MHC.
- 4 factors that determine an Individual response to an immunogen:
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-Genotype
-Quantity/frequency of administration
-Route of administration
-Use of adjuvant - What difference does genotype make in an individual's response to immunogens?
- MHC is pleomorphic; some individuals respond to Ag better than others.
- How does quantity/frequency affect reaction to an immunogen?
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Quantity - must have enough to elicit a response;
Frequency - boosters/secondary response will have a greater response - 3 routes of Immunogen administration:
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-IV
-Intradermal (into skin)
-Subdermal (just under skin)
-Intramuscular
-Intraperitoneal - 4 effects of an Adjuvant:
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1. prolong Ag persistence
2. Enhance co-stimulatory signals
3. Induce inflammation (form granuloma)
4. Stimulate lymphocyte proliferation. - what is an Immunodominant epitope?
- one that elicits a stronger response than other epitopes on the same protein/molecule.
- What antibodies respond when immunizing with a hapten-carrier conjugate?
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-Anti-hapten Ab -> most if this is the immunodominant epitope on the complex.
-Anti-carrier+hapten Ab
-Anti-carrier Ab