Lecture 9 - MHC Flashcards Preview

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Flashcards in Lecture 9 - MHC Deck (37):
1

What does the TCR recognise?

The combined shape of the MHC and antigen

2

Number of extracellular domains possessed by MHC

Four

3

Is the b2-microglobulin gene in the HLA locus?

No
On a different chromosome

4

Is the b2-globulin chain covalently linked to MHCI?

No

5

Length of peptides recognised by TCR

8-12aa

6

Regions making up MHCI peptide-binding region

Alpha1, alpha2

7

Regions making up MHCI Ig-like domain

Alpha3, B2-mocroglobulin

8

Size of alpha1, alpha2 and alpha3 domains

Each is 90aa

9

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

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

10

Shape of peptide-binding cleft

Base of beta sheets
Surrounded by two alpha helices

11

Chains of MHCI

Heavy chain - alpha1, alpha2, alpha3
Light chain - b2-microglobulin

12

MHCII structure

No heavy or light chains
Two equal chains, one made of alpha1, alpha2, the other made from beta1, beta2

13

Antigen-binding site of MHCII

Alpha1, beta1

14

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

No

15

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

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

16

At what orientation does TCR bind to MHC?

At a diagonal angle
Ensures maximum contact

17

Does TCR contact mostly MHC or antigen?

TCR makes most contact with MHC surface

18

TCR specificity

Specific to both antigen and MHC

19

Does MHC expression change in cells?

Yes.
Upregulation during immune response

20

MHC human locus

Human Leukocyte Antigens (HLA) locus

21

Mouse MHC locus

H-2 locus

22

Structure of human HLA locus

2 regions, each with 3 genes
1 region is MHCII, 1 region is MHCI

23

HLA MHCII genes

DP
DQ
DR

24

HLA MHCI genes

B
C
A

25

H-2 locus structure

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

26

H-2 locus class I genes

K
D

27

H-2 locus class II genes

I-A
I-E

28

Genes in I-A and I-E regions

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

29

Genes in K and D regions of H-2

K has one alpha gene
D has two alpha genes

30

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

Gene duplication and divergence

31

How are MHC alleles expressed?

Codominantly
Both alleles (one from each parent) are expressed

32

Location of HLA locus

Chromosome 6

33

Location of b2-microglobulin gene

Chromosome 15

34

Maximum number of MHCI types expressible on a cell surface

6 (3x different types on each chromosome)

35

Minimum number of MHCI types expressible on a cell curface

3
If B, C and A are homozygous

36

Which MHC has more variety?

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

37

Outcome of MHC polymorphism

Allows or prevents binding by certain TCRs