Lecture 9 - MHC

Question 1

What does the TCR recognise?

Answer 1

The combined shape of the MHC and antigen

Question 2

Number of extracellular domains possessed by MHC

Answer 2

Four

Question 3

Is the b2-microglobulin gene in the HLA locus?

Answer 3

No

On a different chromosome

Question 4

Is the b2-globulin chain covalently linked to MHCI?

Answer 4

No

Question 5

Length of peptides recognised by TCR

Answer 5

8-12aa

Question 6

Regions making up MHCI peptide-binding region

Answer 6

Alpha1, alpha2

Question 7

Regions making up MHCI Ig-like domain

Answer 7

Alpha3, B2-mocroglobulin

Question 8

Size of alpha1, alpha2 and alpha3 domains

Answer 8

Each is 90aa

Question 9

Regions of an MHC molecule
1)
2)
3)
4)

Answer 9

1) Antigen-binding region
2) Ig-like region
3) Transmembrane region
4) Cytoplasmic region

Question 10

Shape of peptide-binding cleft

Answer 10

Base of beta sheets

Surrounded by two alpha helices

Question 11

Chains of MHCI

Answer 11

Heavy chain - alpha1, alpha2, alpha3

Light chain - b2-microglobulin

Question 12

MHCII structure

Answer 12

No heavy or light chains

Two equal chains, one made of alpha1, alpha2, the other made from beta1, beta2

Question 13

Antigen-binding site of MHCII

Answer 13

Alpha1, beta1

Question 14

Are the alpha1 and beta1 regions of the MHCII antigen-binding cleft covalently linked?

Answer 14

No

Question 15

Differences between MHCI and MHCII
1)
2)
3)
4)

Answer 15

1) MHCI has b2-microglobulin
2) MHCI has a heavy and light chain. MHCII has two equal-length transmembrane proteins.
3) MHCI interacts with CD8. MHCII interacts with CD4
4) MHCII can bind slightly larger proteins than MHCI

Question 16

At what orientation does TCR bind to MHC?

Answer 16

At a diagonal angle

Ensures maximum contact

Question 17

Does TCR contact mostly MHC or antigen?

Answer 17

TCR makes most contact with MHC surface

Question 18

TCR specificity

Answer 18

Specific to both antigen and MHC

Question 19

Does MHC expression change in cells?

Answer 19

Yes.

Upregulation during immune response

Question 20

MHC human locus

Answer 20

Human Leukocyte Antigens (HLA) locus

Question 21

Mouse MHC locus

Answer 21

H-2 locus

Question 22

Structure of human HLA locus

Answer 22

2 regions, each with 3 genes

1 region is MHCII, 1 region is MHCI

Question 23

HLA MHCII genes

Answer 23

DP
DQ
DR

Question 24

HLA MHCI genes

Answer 24

B
C
A

Question 25

H-2 locus structure

Answer 25

2 class II genes flanked by 2 class I genes (1 on each side)

Question 26

H-2 locus class I genes

Answer 26

K | D

Question 27

H-2 locus class II genes

Answer 27

I-A | I-E

Question 28

Genes in I-A and I-E regions

Answer 28

I-A and I-E each have an alpha chain and a beta chain gene

Question 29

Genes in K and D regions of H-2

Answer 29

K has one alpha gene | D has two alpha genes

Question 30

Why does the D region of H-2 have two alpha chain genes?

Answer 30

Gene duplication and divergence

Question 31

How are MHC alleles expressed?

Answer 31

``` Codominantly Both alleles (one from each parent) are expressed ```

Question 32

Location of HLA locus

Answer 32

Chromosome 6

Question 33

Location of b2-microglobulin gene

Answer 33

Chromosome 15

Question 34

Maximum number of MHCI types expressible on a cell surface

Answer 34

6 (3x different types on each chromosome)

Question 35

Minimum number of MHCI types expressible on a cell curface

Answer 35

3 | If B, C and A are homozygous

Question 36

Which MHC has more variety?

Answer 36

MHCII Alpha and beta chains can be promiscuous Stability of hybrids isn't favourable, so most MHC on cell surface are unhybridised

Question 37

Outcome of MHC polymorphism

Answer 37

Allows or prevents binding by certain TCRs