Lecture 9 - MHC Flashcards

1
Q

What does the TCR recognise?

A

The combined shape of the MHC and antigen

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2
Q

Number of extracellular domains possessed by MHC

A

Four

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3
Q

Is the b2-microglobulin gene in the HLA locus?

A

No

On a different chromosome

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4
Q

Is the b2-globulin chain covalently linked to MHCI?

A

No

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5
Q

Length of peptides recognised by TCR

A

8-12aa

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6
Q

Regions making up MHCI peptide-binding region

A

Alpha1, alpha2

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7
Q

Regions making up MHCI Ig-like domain

A

Alpha3, B2-mocroglobulin

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8
Q

Size of alpha1, alpha2 and alpha3 domains

A

Each is 90aa

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9
Q
Regions of an MHC molecule
1)
2)
3)
4)
A

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

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10
Q

Shape of peptide-binding cleft

A

Base of beta sheets

Surrounded by two alpha helices

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11
Q

Chains of MHCI

A

Heavy chain - alpha1, alpha2, alpha3

Light chain - b2-microglobulin

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12
Q

MHCII structure

A

No heavy or light chains

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

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13
Q

Antigen-binding site of MHCII

A

Alpha1, beta1

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14
Q

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

A

No

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15
Q
Differences between MHCI and MHCII
1)
2)
3)
4)
A

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

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16
Q

At what orientation does TCR bind to MHC?

A

At a diagonal angle

Ensures maximum contact

17
Q

Does TCR contact mostly MHC or antigen?

A

TCR makes most contact with MHC surface

18
Q

TCR specificity

A

Specific to both antigen and MHC

19
Q

Does MHC expression change in cells?

A

Yes.

Upregulation during immune response

20
Q

MHC human locus

A

Human Leukocyte Antigens (HLA) locus

21
Q

Mouse MHC locus

A

H-2 locus

22
Q

Structure of human HLA locus

A

2 regions, each with 3 genes

1 region is MHCII, 1 region is MHCI

23
Q

HLA MHCII genes

A

DP
DQ
DR

24
Q

HLA MHCI genes

A

B
C
A

25
Q

H-2 locus structure

A

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

26
Q

H-2 locus class I genes

A

K

D

27
Q

H-2 locus class II genes

A

I-A

I-E

28
Q

Genes in I-A and I-E regions

A

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

29
Q

Genes in K and D regions of H-2

A

K has one alpha gene

D has two alpha genes

30
Q

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

A

Gene duplication and divergence

31
Q

How are MHC alleles expressed?

A
Codominantly
Both alleles (one from each parent) are expressed
32
Q

Location of HLA locus

A

Chromosome 6

33
Q

Location of b2-microglobulin gene

A

Chromosome 15

34
Q

Maximum number of MHCI types expressible on a cell surface

A

6 (3x different types on each chromosome)

35
Q

Minimum number of MHCI types expressible on a cell curface

A

3

If B, C and A are homozygous

36
Q

Which MHC has more variety?

A

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

37
Q

Outcome of MHC polymorphism

A

Allows or prevents binding by certain TCRs