CHP 6 - T cell antigen recognition Flashcards
When do effector cells generate?
During clonal selection
Where does MHC diversity generate from?
Due to MHC gene families and genetic polymorphism, it is not due to recombination like T cell receptor and B cell.
What are the two types of functions of the genes that are activated from the T cell receptor MHC peptide complex?
1) for T cell to undergo proper division and differentiation
2) Genes required to carry out the effector functions of the activated T cell
Cytotoxic cells are activated ______ T cell that target cells that are infected with _____________ pathogens
CD8; intracellular
Helper T cells are activated ________ T cells that activate cells that combat ____________ pathogens.
CD4; extracellular
What does the T cell receptor lack? – must need other cell surface molecules to do this
lacks the ability to initiate intracellular signaling events on its own due to lack of cytoplasmic domain
CD28 is an essential costimulatory signal for naive T cell activation by resulting in a (+/-) signal
Positive
CTLA4 binds to __________ on a APC and down regulates T cell activation
CD80/86
CD28 and CTLA4 compete for _______ and ________ binding
Cd80 and Cd86
Binding of CTLA4 and CD80/CD86 results in which type of signaling?
Negative
The alpha chain of MHC I anchors MHC to?
Plasma membrane
The peptide binding groove binds peptides that are ___ to ____ amino acids long
8 to 10
What quality do MHC receptors have to allow a single MHC molecule to bind to a variety of peptides?
Promiscuous binding specificity
Somatic recombination of T cell receptor chains can result in?
Productive rearrangement or unproductive rearrangement
CD8 molecule makes contact with structural domain of the ___-subunit of MHC class I
Alpha
When the alpha chain of MHC I enters the ER, what molecule interacts with MHC to chaperone and assist in the addition of B2-microglobulin?
Calnexin
What is the function of tapsin?
1) allows efficient peptide loading on MHC I class
2) promotes association of peptide that can bind tightly to MHC class I
What is the function of calreticulin in regard to MHC class I loading?
promotes proper assembly of MHC class I molecules with the tightly bound peptide
Which molecule is responsible for keeping MHC class I molecule in the ER until they have become properly folded?
Calnexin
Which molecule is responsible for cleaving intracellular proteins into small peptides of varying lengths?
Proteasome
Cytokines secreted during an inflammatory response can produce?
immunoproteasome
Which molecule is responsible for transportation of peptides into the ER membrane?
Transporter associated with antigen processing (TAP)
What is peptide trimming? Which molecule is responsible for this?
The removal of amino acids from a peptide – protease ERAP trims the N-terminal
Endoplasmic reticulum aminopeptidase
Which molecule is responsible for ensuring the tight bounding of peptides in the peptide binding groove?
Tapasin
What are the five major steps for peptide loading onto a MHC molecule?
1) Formation of the peptide loading complex (MHC)
2) Digestion of proteins by proteasome
3) Peptide transportation to the ER
4) Peptide trimming to ensure tight binding between MHC and antigen
5) Transportation of MHC-peptide complex to the plasma membrane for presentation
What is the one major difference between MHC I class peptide loading vs MHC II class peptide loading?
MHC class I peptide loading occurs in the ER
MHC class II peptide loading occurs outside the ER in a vesicle (secretory pathway)
MHC class II are not capable of loading peptide until they are part of a vesicle capable of fusing with a ________________.
Phagolysosome
What are the four steps of MHC II loading?
1) MHC class II molecule assembly in the ER
2) Clip production
3) Phagocytosis and fusion with the MHC compartment
4) Peptide loading
Which protein is responsible for assembling the MHC II molecule in the ER and blocks the peptide binding groove?
Invariant chain
Which protease cleaves the invariant chain and leaves CLIP bound on the peptide-binding groove?
Cathepsin S
Which antigen promotes the exchange of CLIP for lysosomal peptides?
HLA-DM
What is MHC cross presentation?
One cell having the ability to stimulate both CD4 and CD8 T cells at any time.
Which type of cell is known for being an expert at MHC cross presentation?
Dendritic cells
