Antigens Flashcards
What does the innate immune system recognize?
PAMPS - pathogen associated molecular patterns
What does the adaptive immune system recognize?
Antigens
Define antigen
Any molecule that can interact specifically with the immunoglobulin (Ig) receptor of B-cells or the T-cell receptor complexed with MHC
Do all molecules induce immunity?
No
What is an immunogen?
A molecule that induces a specific immune response
Are all antigens immunogens?
No
Are all immunogens antigens?
Yes
Humoral Immunogens
(B cells)
Cell mediated Immunogens
T cells
Are proteins recognized directly?
No
How can we recognize proteins?
Peptides processed from the protein are seen in association w MHC molecules
What are the 4 properties of an immunogen?
- Foreignness
- Molecular size
- Chemical Heterogeneity
- Degradability
To serve as an immunogen, a molecule must be seen as “….”?
Non-self
What is the degree of immunogenicity dependent on?
The degree of foreignness
The greater phylogenic distance b/w species typically means what?
Greater the chance of immunogenicity
What are 2 exceptions to foreigness?
- Highly conserved molecules like collagen or cytochrom c may not be immunogenic even in distant species
- Some self molecules may sequester an immune response (sperm or lens tissue) in animal they came from
Is there a correlation b/w size and immunogenicity?
Yes, there is a sweet spot
What are the best immunogens in the range of?
100,000 Da
Small molecules - what size? are generally poor immunogens
5-10,000
Will size alone make a good immunogen?
No, the more complex the better
Are sythentic homopolymers immunogenic?
No, they are boring we want complex
How do we increase immunogenicity in terms of chemial heterogeneity?
Proteins w more complexity in primary structure and those showing secondary, tertiary, and quaternary structure
What do we have to do to proteins in roder for them to be presented by MHC to activate Tcells?
Degrade proteins
Why is an insoluble antigen better than a soluble?
Insoluble is more likely to be phagoctosed & processed
Is a large or small antigen better?
Large - more processing, more epitopes
Substances that are injected Ag serve to..
enhance the immunogenicity
What 3 things do adjuvants do?
- Stimulate immune response
- Prolong Exposure to Ag
- Co-stimulatory signal
Freund’s
Freund’s adjuvant is a solution of antigen emulsified in mineral oil and used as an immunopotentiator (booster)
What is Freund’s adjuvant composed of?
is composed of inactivated and dried mycobacteria
What part of the adjuvant stimulates macrophage activity
Heat killed mycobacteria
What two things bind and precipitate the Ag to keep it in the system longer and allow for slow release of Ag
Alum and Freunds adjuvant
How long does the adjuvant increase the time of exposure of the Ag?
From a few days to a few weeks
How does precipitation facilitate phagocytosis?
Increase the size
When the cells are stimulated by the Ag they require a second co-stimulatory response, what up-regulates this?
Freund’s adjuvant, LPS
