MHC 2 Flashcards
Does MHC class II have a restriction on how long the peptides it holds can be?
No
Why is there not a restriction on the length of the peptides that can be held by MHC class II?
They can overhand at the end of the peptide binding group
Where do peptides presented on MHC class I generally come from?
Intracellular proteins
Example of the origin of a peptide that may be expressed on MHC class I?
A virus–> virus replicates inside our cells and produces viral proteins intracellularly
Where do peptides presented on MHC class II generally come from?
Extracellular proteins
Example of the origin of a peptide that may be expressed on MHC class II?
Bacterium–> phagocytosed by a cell and the peptides are processed
What type of cells express MHC class I?
Almost all of the cells
What type of cells express MHC class II?
Professional antigen presenting cells
Which type of cell expresses neither MHC class?
RBCs
Why may some parasites hide in RBCs?
They dont present any MHC
Which cells express large amount of MHC class I and II?
B cells and Dendritic cells
What does the proteosome do?
Cleave large proteins into 12-13 AA segments
What can be done to the proteasome during an infection?
It can be altered to form an immunoproteosome
What does the TAP transporter do?
Facilitates the transport of proteins from the cytoplasm to the lumen of the ER
What does TAP stand for?
Transporter associated with antigen processing
Where do MHC class I molecules assemble?
In the ER
Where are membrane proteins assembled?
ER
What is MHC class I associated with in the ER, before it associates with beta 2 microglobulin?
Calnexin
What happens when the MHC class I molecule associates with beta 2 microglobulin?
It no longer associates with calnexin, and instead interacts with tapasin, and ERP 57, and calreticulin
Role of tapasin?
Interacts with both the MHC class I and the tap transporter–> bring MHCI to the vicinity of the TAP transporter
Where do the MHC class I remain if they dont have a peptide bound?
ER
Why do MHC class I remain in the ER if they dont have a peptide?
The chaperone proteins (ER57 and calreticulin) that ti is associated with keep it there
What happens if a peptide is loaded onto the MHC class I from a TAP transporter?
The chaperons wont recognise it as an unfolded protein, and so will let the MHCI leave the ER
How does the MHCI reac the cell surface once it has acquired a peptide sequence?
via the golgi
