Flashcards in Antigen processing, presentation & Co- stimulation Deck (51)
CD8+ T cells are _______ restricted and recognize ________ proteins.
CD4+ T cells are _______ restricted and recognize _______ and _______ pathogens.
Extracellular & Intravesicular
What are the 4 steps of lymphocyte activation?
1. Microbe infects host
2. microbe is taken up by APC (antigen presenting cell) at site of infection
3. APC enters lymph circulation and into Lymph node
4. Naive T and B cells enter Lymph node from circulation.
_______ is central to the development of immune response.
What is Antigen presentation?
It is the bridge between recognition and full blown immune response.
- Enables T cell-mediated killing, or augments antibody production by B cells.
True or false, antigen presentation is context dependent?
True! deploys different immune responses under different circumstances.
Antigen presentation is modulated by _________.
Successful antigen presentation results in what?
Activation of T cells
What are the most effective Antigen presenting cells for initial T cell activation?
_________ must be activated by phagocytes before presenting antigens.
_______ may be the major type of antigen presenting cell for secondary immune response.
What can happen if antigen recognition occurs without antigen presentation?
Tolerance = not good!
What is the "professional" APC?
True or false, Dendritic cells, B & T cells are the only APC's.
- All nucleated cells can present endogenous antigen in association with MHC I molecules.
What are the two pathways of antigen presentation?
Pathway 1 = Exogenous antigens presented to T helper cells.
Pathway 2 = Endogenous antigens presented to CD8+ T cells
Define antigen processing...
process of antigens being digested and placed of surface with correct MHC molecules.
What are the steps of the Endogenous antigen Cytosolic pathway?
- Proteins to be degraded are tagged by ubiquitin
- Degradation of ubiquitin-protein complexes occur within the central channel or proteasome.
- Peptides generated are transported into the Lumen of RER by TAP's
- Newly synthesized MHC within RER membrane binds to antigen peptide.
- Antigen-MHC I complex released and transported to the cell.
What are the steps of the Exogenous antigen Endocytic pathway?
- Antigens are internalized in endosomes
- They are digested first in the endosomes, then in lysosomes to 13-18 aa peptides.
- Class II molecules are produced at RER
- They are associated with the invariant chain protein, preventing their binding to endogenous antigens.
- Class II-Ii complex move into endocytic compartments
- Ii will be digested to a short fragment (CLIP)
- HLA-DM triggers the exchange of CLIP and antigen peptide.
- HLA-DO block the activity of HLA-DM
_____ is two distinct polypeptides, an alpha and a beta.
______ is one alpha peptide.
What is a haplotype and what does it influence?
a cluster of alternative form of same gene, closely linked on same chromosome. Influences:
- How individual responds to pathogens
- Susceptibility to certain diseases
- Transplant success
MHC genes are highly polymorphic.... what does this mean?
- Hundreds of alleys in humans apron. 10^13 combinations (This is why its hard to match ppl for transplants, even 1st relatives often differ.)
MHC alleles are _______ expressed.
Self MHC + foreign AG = ?
T cell response
Self MHC + Self Ag = ?
MHC expression can be induced on almost every nucleated cell in the body....True or False?
______ is a key factor in determining tissue matching for a transplant donor and recipients.
True or false, MHC molecules have very limited specificity.
False, its very broad!
MHC molecules have a ______ on/off rate.