MHC and antigen presentation

Question 1

How do T cells function?

Answer 1

By making contact with other cells and inducing them to change

Question 2

What part of the MHC molecule does CD8 bind?

Answer 2

alpha 3 domain of MHC class I

Question 3

What part of the MHC molecule does CD4 bind?

Answer 3

beta 2 domain of MHC class II

Question 4

How are peptide bound in the MHC peptide groove?

Answer 4

Hydrogen bonds and ionic interactions

Question 5

What type of groove does type I have?

Answer 5

Groove closed - peptides bound in pockets at ends of groove

Question 6

What type of groove does type II have?

Answer 6

Groove open - peptides bound along their length

Question 7

What do peptides bound to MHC class I have?

Answer 7

Conserved anchor residues at ends - specific for each MHC isoform

Question 8

Peptides for MHC class II come from what type of source?

Answer 8

Extracellular antigen

Question 9

Peptides for MHC class I come from what type of course?

Answer 9

Intracellular antigen

Question 10

Where are cytosolic proteins degraded?

Answer 10

Proteasome

Question 11

What alters proteosome structure?

Answer 11

Infection (induced by IFNgamma) - constitutive proteasome into immunoproteasome

Question 12

What happens to cytosolic proteins after they’re degraded?

Answer 12

Transported into ER via TAP

Question 13

What stabilises MHC class I before beta2-microglobulin binds?

Answer 13

Calnexin

Question 14

What does the peptide loading complex consist of?

Answer 14

Class I heavy chain, beta2-microglobulin, calreticulin, rapasin, TAP and ERp57

Question 15

What is the role of tapasin?

Answer 15

Positions MHC class I to receive peptides and keeps the binding pocked in an open conformation

Question 16

What is peptide editing?

Answer 16

When peptides are trimmed by aminopeptidases (ERAP) to ensure a good fit

Question 17

What blocks the binding of peptides to class II molecules in the ER

Answer 17

Invariant chain

Question 18

What happens to the invariant chain in vesicles?

Answer 18

Cleaved - leaving CLIP fragment bound which blocks peptide binding to class II in vesicles

Question 19

What facilitates the release of CLIP and allows peptides to bind?

Answer 19

HLA-DM

Question 20

What is cross presentation?

Answer 20

Done by class I molecules - rare event seen in viral infection where macrophages phagocytose infected cells

Question 21

What type of cells are you most likely to find class I

Answer 21

Nucleated cells

Question 22

What type of cells are you most likely to find class II

Answer 22

APCs

Question 23

What influences the expression levels of MHC

Answer 23

Cytokines

Question 24

Where is the variation in MHC allotypes concentrated?

Answer 24

At antigen binding sites

Question 25

What represents selective pressure for MHC diversity?

Answer 25

Infectious diseases

Question 26

How are new MHC alleles generated?

Answer 26

Interallelic conversion between same/ different genes