MHC Presentation

Question 1

How does MHC class 1 work?

Answer 1

• Peptides from cytoplasm are bought to ER to bind MHC 1
• combo brought to cell-surface
• small percentage of all cytoplasm proteins cut into peptides for this
• so, non-self peptides recognized from the outside

Question 2

How does MHC class 2 work?

Answer 2

• takes peptides from endosome

- gives a picture of proteins the cell has picked up from outside

Question 3

Which cells express MHC class 2?

Answer 3

professional APCs

Question 4

Differences between class 1 and 2 binding sites

Answer 4

Class 1
- peptide must fit in groove (8-11 peptides)
anchored at ends

Class 2

• peptides can be longer than groove (13-25 aa)
• anchors are spaced along the binding groove

Question 5

How does the TCR interact with the MHC?

Answer 5

interacts with antigen binding groove of MHC

Question 6

On which cells is MHC 1 found?

Answer 6

CD8 T cells

Question 7

On which cells in MHC 2 found?

Answer 7

CD4 T cells

Question 8

Describe MHC class 1 display of peptides

Answer 8

• generation of peptide by proteosome
• transport of peptide into ER by TAP transporter
• binding of peptide to MHC class 1 binding groove

Question 9

Describe MHC class 2 display of peptides

Answer 9

• antigen phagocytized and degraded
• cleaved into peptides in phagosome/endosome
• MHC class 2 brought to collect peptides (must pass through ER, where class 1 binding peptides are present)
• invariante chain binds partly in peptide froove and prevents these peptides from bidning class 2
• invariant chain is cleaved by endosome, leaving peptide (CLIP) in the peptide groove
• CLIP removed by DM and replaced with antigenic peptide

Question 10

What happens in an invariant chain knockout mouse?

Answer 10

MHC class 2 molecules are not properly exported without invariant chain
MHC class 2 expression is low and there are few CD4 T cells

Question 11

Define a locus

Answer 11

an array of genes along a chromosome

Question 12

Define a haplotypes

Answer 12

an array of alleles of a locus

Question 13

Devisions of mouse MHC (H-2)

Answer 13

Class 1
-K,D,L

Class 2
-A,E

Question 14

Divisions in human MHC (HLA)

Answer 14

Class 1
-A,B,C

Class 2
- DP,DQ,DR

Question 15

Why are there haplotypes for H2 and not HLA?

Answer 15

• recombination between genes is high
• no inbred humans
• no equivalent in people
• in inbred mice, obvious linkages