Antigen presentation

Question 1

MHC 2 origination

Answer 1

MHC 2 molecules are produced and exported from the ER in vesicles.

Question 2

MHC class 2 block/way to prevent unwanted interactions

Answer 2

The invariant chain li, CD74 prevent peptides from binding to the groove too early in ER
it is initially degraded by proteolytic activity within the endocytic compartments and becomes CLIP
The CLIP fragment is in the peptide groove preventing unwanted binding.

Question 3

How is CLIP removed from HMC 2

Answer 3

Once MHC2 and clip reach a vesicle with exogenous peptides HLA-DM binds to MHC2 releasing CLIP.
HLA-DM keeps MHC stable and open, once peptide with high affinity binds HLA-DM dissociates
ensures that only strongly bound peptides attach and are expressed on the cell surface

Question 4

What does HLA-DO do

Answer 4

Binds to HLA-DM and prevents it from binding to MHC 2
this prevents peptides from being loaded on MHC 2 and limits antigen presentation.
In inflammation HLA-DM is increased but HLA-DO is not

Question 5

T-Cell main paradigms

Answer 5

Origination from bone marrow progenitors
Activation- antigen receptor and second signaling from APCs that provide CD28
Effector functions

Question 6

T-cell receptor genes and expression

Answer 6

T-cells are defined by expression of T-cell Receptor (TCR)
Main receptor that binds to MHC complexed with peptide, only binds to self MHC plus cognate peptide.

Question 7

TCR

Answer 7

Very similar to the B-cell receptor
has variable and constant regions
undergoes recombination with VDJ segments
has tiny cytoplasmic tails
cannot be secreted/circulate in blood, only bound to membrane of T-cells

Question 8

Most common class of T-cells

Answer 8

Alpha:Beta T-cells
also has Gamma: Delta but low frequency in adults.