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x- Immunology MICR 3230 > Major Histocompatibility Complex/ Antigen Presentation > Flashcards

Major Histocompatibility Complex/ Antigen Presentation Flashcards

1
Q

What cells only recognize antigens presented on the surface of other cells?

A

T-cells

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2
Q

How are antigens presented on the surface of cells?

A

MHC molecule

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3
Q

Do BCRs/ antibodies need antigen presented on MHC to be recognized?

A

no- can interact with free-floating antigen
- unlike T-cells, need bound

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4
Q

How are T-cells presented with antigens?

A

MHC

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5
Q

What binds to the MHC molecule inside cell?

A

antigen

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6
Q

How is antigen presented on MHC cell surface?

A

digestion/ complex transported

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7
Q

What are professional APC’s?

A

Dendritic cells
Macrophages

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8
Q

What act as “cell surface vessels”?

A

MHC molecules

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9
Q

Where is antigen binding to MHC molecules generated?

A

inside cell

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10
Q

What hold/ display fragments of antigen so T-cells can interact with their TCRs?

A

MHC (cell surface vessel)

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11
Q

How are MHC genes spread within the population?

A

alleles inherited
-contribute to individual response to infection/ disease susceptibility/ autoimmunity development

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12
Q

How do MHC molecules attach to cell membrane?

A

transmembrane segment- stability

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13
Q

What are the 2 classes of MHC molecules?

A

MHC I
MHC II

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14
Q

Where on the MHC does the antigen bind?

A

Peptide-binding groove

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15
Q

How many transmembrane domains does MHC class I molecule have?

A

1

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16
Q

How many transmembrane domains does MHC class II domain have?

A

2

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17
Q

What MHC molecule has 3 alpha domains and
1 B-microglobulin domain?

A

MHC I

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18
Q

What MHC molecule has a narrow/ shallow peptide binding groove?

A

MHC I

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19
Q

What MHC molecule is involved in self-peptide recognition?

A

MHC I

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20
Q

What MHC molecule is constitutively expressed?
(always expressed- screening)

A

MHC I

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21
Q

What MHC molecule is associated with 2 globulin structures (1 alpha/ 1 beta side) ?

A

MHC II
B1+B2 / a1+a2

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22
Q

What MHC molecule has a deep peptide binding groove (goes all way through)?

A

MHC II

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23
Q

What term describes peptide/ antigen binding?

A

variable

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24
Q

How many different peptides can an MHC molecule bind?

A

numerous

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25
Q

What makes up the MHC I peptide-binding domain?

A

a1/a2

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26
Q

What makes up the MHC II peptide-binding domain?

A

a1/B1

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27
Q

What MHC molecule is closed at both ends (shorter)?

A

MHC I

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28
Q

What MHC molecule is open at both ends?

A

MHC II

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29
Q

What MHC molecule do larger peptides bind to?

A

MHC II

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30
Q

What T cell does MHC class I present peptides to?

A

CD8+

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31
Q

Why does MHC I bind peptides from intracellular sources?

A

recognizes self-antigens/ peptides

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32
Q

How long are the peptides bound to MHC I?

A

8-10 AA

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33
Q

What are the specific amino acids at key locations in MHC I bound peptide?

A

Anchor residues

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34
Q

What T cell does MHC class II present peptides to?

A

CD4+

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35
Q

What peptides does MHC II bind?

A

extracellular/ variety

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36
Q

How long are the peptides bound to MHC II?

A

13-18 AA

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37
Q

Peptides bound to which MHC class are less conserved?- greater variability (sequence/ length)

A

MHC II

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38
Q

What are other names for MHC?

A

HLA = human leukocyte antigen
H2 =mice

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39
Q

What AA are the same/ specific between all MHC class I proteins?

A

anchor point = anchor residues

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40
Q

What is a common problem for antigens/ receptors?

A

bind wide variety antigens with strong affinity

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41
Q

What 2 combinations allow MHC molecules to bind an antigen?

A

Peptide-binding promiscuity
expression of different MHC variants on each cell

42
Q

Why are MHC variants/ peptide-binding promiscuity important?

A

maximize recognition of different epitopes of antigen

43
Q

What are parts of antigen that are recognized?

A

Epitopes

44
Q

What are the 3 classes MHC genes are organized into?

A

I/ II/ III

45
Q

What are the 2 kinds of MHC genes?

A

Classical
Non-classical

46
Q

What MHC classes are classical?

A

I/ II

47
Q

What MHC classes are non-classical?

A

III

48
Q

Why are MHC class III genes non-classical?

A

no direct role in presenting antigens to T cells
- indirect immune functions

49
Q

What MHC molecule is associated with cytotoxic T cells?

A

MHC I = CD8 = cytotoxic T

50
Q

What MHC molecule is associated with helper T cells?

A

MHC II = CD4 = T helper

51
Q

Where are the glycoproteins of MHC I expressed?

A

surface of nucleated cells
(neutrophils/ platelets)

52
Q

Where are the glycoproteins of MHC II expressed?

A

surface of APCs
= dendritic cells/ macrophages

53
Q

What MHC molecule is primarily present on exogenous/ extracellular peptides/ antigens?

A

MHC II

54
Q

What MHC classes are glycoproteins?

A

I/ II = glycoproteins
III = diverse set proteins

55
Q

What are immune functions of MHC class III?

A

encode complement proteins- C4/C2/ factor B
inflammatory cytokines - TNF

56
Q

What are 2 consequences of disruption to MHC III?

A

susceptibility to infectious diseases
autoimmune diseases (chrohns/ MS)
- constant/overproduction inflammatory cytokines

57
Q

What is the term when many alternate forms of each gene are in a population?

A

Polymorphic

58
Q

What is the term for alternate forms of genes?

A

Alleles

59
Q

What is the inherited set of linked alleles termed?

A

Haplotype

60
Q

How is a set of MHC genes inherited?

A

set alleles inherited as 1 unit, from each parent
= Haplotype

61
Q

Why is there not a lot of MHC gene recombination?

A

tightly linked

62
Q

What 2 terms describes MHC genes?

A

highly polymorphic
tightly linked

63
Q

How are MHC molecules expressed?

A

Co-dominantly

64
Q

What is it when both maternal/ paternal haplotypes are expressed at same time?

A

Co-dominance

65
Q

What allows a cell to present a large # of different peptides?

A

expression of different MHC I molecules
- each different binding affinities

66
Q

How many MHC I molecules are there?

A

6

67
Q

How many MHC II molecules are there?

A

12

68
Q

What is the term for containing multiple genes with the same function but slightly different structures?

A

Polygenic

69
Q

How are host cells displayed as healthy?

A

self MHC I/ self-peptide display

70
Q

How can a foreign protein show host cell is infected? MHC I

A

MHC I peptide display- activate T-cytotoxic cells

71
Q

How can a foreign protein show host cell is infected? MHC II

A

MHC II peptide display- activate T-helper cells

72
Q

How are T cells tested?

A

MHC I/ II display self-peptides
- test for autoreactivity

73
Q

Where are t-cells tested for autoreactivity?
(positive/ negative selection)

A

primary lymphoid organ = thymus

74
Q

How is tolerance to self-proteins done in secondary lymphoid tissues?

A

display self peptide MHC I/ II

75
Q

What MHC molecule is constitutively expressed?

A

MHC I

76
Q

How/ where is MHC II expressed?

A

variable/ on limited cells (APC)

77
Q

What is MHC II expression controlled by?

A

genetic regulatory components
viral interference
cytokine-mediated signalling

78
Q

What effect does cytokine binding to receptors have on MHC II expression on APCs?

A

increases

79
Q

What effect do genetic regulatory components have on MHC expression?

A

induce signal transduction cascades

80
Q

What effect does viral interference have on antigen presentation via MHC I?

A

inhibit

81
Q

When can CD4+/ CD8+ recognize an antigen?

A

only when presented in groove of MHC

82
Q

What must match for recognition? (APC/ T cell)

A

MHC haplotype

83
Q

What happens if you fix/ block MHC molecule on APC?

A

antigen can not bind/ no t cell recognition

84
Q

What MHC is associated with endogenous antigens?

A

MHC I

85
Q

How are endogenous antigens processed?

A

cytosolic/ endogenous pathway

86
Q

How are exogenous antigens processed?

A

exogenous pathway

87
Q

How are exogenous antigens presented on APC membrane?

A

MHC II

88
Q

Where are endogenous antigens generated?

A

within cell

89
Q

Where are exogenous cells generated/ taken up?

A

taken up from extracellular environment
- via endocytosis

90
Q

What is an example of MHC II antigen?

A

bacteria/ fungus

91
Q

How are intracellular proteins degraded into peptides?

A

by proteosome

92
Q

How are proteins tagged for degradation? (protein-peptide)

A

ibiquitin

93
Q

What can activated infected cells temporarily express?

A

immunoproteosome

94
Q

What proteins in the cytosolic protein pool are degraded by proteosomes?

A

those tagged by ibiquitin

95
Q

What are the 3 steps in the endogenous pathway?

A
  1. proteolytic cleavage by proteasome
  2. peptide transport to cytosol to RER
  3. chaperones aid peptide- assembly with MHC
96
Q

What does MHC I present on?

A

nucleated cells- includes APCs

97
Q

What are the steps in exogenous pathway?

A
  1. receptor-mediated endocytosis
  2. degradation to peptides
  3. interaction between MHC II/ peptide
  4. antigen presentation
  5. interaction peptide/ MHC II
98
Q

What is the term when an antigen acquired by exogenous pathway is redirected to endogenous pathway so peptides presented on MHC I?

A

cross-presentation

99
Q

What are some non-peptide antigens?

A

small lipid containing antigens
small molecules/metabolites

100
Q

What is different in MHC I for non-peptide antigens?

A

peptide-binding groove
CD1 protein class ex- MR1

x- Immunology MICR 3230 (11 decks)

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