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VBSC 211: The Immune System > Exam 3: Chapter 5 > Flashcards

Exam 3: Chapter 5 Flashcards

1
Q

What are naïve CD8+ T cells?

A

Cells activated by MHC Class 1 peptides presented by APCs

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2
Q

What are the different forms of any given gene called?

A

Alleles

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3
Q

What is antigen processing?

A

Process in which pathogens and other proteins are chopped up into smaller pieces called peptides

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4
Q

How are the MHC genes arranged on the chromosome?

A

The class 1 and class 2 gene families are in separate regions and are separated by the class 3 region

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5
Q

How do the CDR regions of the TCR contact the peptide MHC?

A

CDRs 1 and 2 bind to the alpha helices of the MHC, and CDR 3 binds the peptide

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6
Q

How many T cell receptors (TCRs) are expressed by each T cell?

A

1

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7
Q

What do chaperone proteins do, in terms of MHC Class 1?

A

Aid in the assembly of the MHC Class 1 heterodimer and facilitate the binding of peptides

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8
Q

What is directional selection?

A

The type of selection that favors one allele over others due to its ability to protect against a pathogen

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9
Q

What are the unique features of helper T cells?

A

They are CD4+ and help activate effector cells to fight extracellular pathogens

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10
Q

What are the specifics of the MHC Class 1 binding pocket?

A

Binds to the ends of peptides, prefers peptides of ~ 9 AAs

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11
Q

In which MHC type does allotype equal isoform?

A

MHC Class 1

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12
Q

What do HLA-E and HLA-G do?

A

Present peptides to NK cells only

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13
Q

Which class region also includes genes involved in the immune response?

A

Class 2

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14
Q

What components form the CD3 complex?

A

2 epsilon domains, 2 zeta domains, 1 delta domain, and 1 gamma domain

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15
Q

What kind of combinatorial diversity is observed in the TCR alpha chain?

A

VJ combination (like the light chain of antibodies)

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16
Q

What is MHC called in humans?

A

Human Leukocyte Antigen Complex (HLA)

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17
Q

How are the binding sites of TCRs determined?

A

By the hypervariable regions, or CDRs

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18
Q

Which MHC class has multiple possible genes for each isotype?

A

Class 2

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19
Q

Compare and contrast the structure of an antibody versus a T cell receptor.

A

Both TCRs and antibodies are made up of variable and constant regions. Antibodies are formed from 4 proteins, while TCRs are formed from 2 proteins. Antibodies can be on the cell surface or secreted, while TCRs are only ever present on cell surfaces

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20
Q

What are the unique features of cytotoxic T cells?

A

They are CD8+, are activated by intracellular pathogens, and kill infected cells

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21
Q

What is degenerate specificity?

A

The ends of the peptide and specific anchor residues are recognized rather than individual peptides, allowing MHCs to bind to a wider variety of peptides

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22
Q

What is the function of the proteosome?

A

To chop proteins into peptides

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23
Q

How are the peptides generated by the proteosome transported into the ER?

A

By the Transporter associated with Antigen Processing (TAP)

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24
Q

What syndrome is associated with TAP mutations?

A

Bare-Lymphocyte Syndrome - less than 1% of the normal amount of Class 1 MHC is present on the cell surface

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25
Q

What do HLA-DP, HLA-DQ, and HLA-DR do?

A

Present peptides to CD4+ T cells

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26
Q

What are alloantibodies?

A

Antibodies produced by a pregnant woman in response to the paternal MHC present within the fetus’s cells

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27
Q

What is gene conversion?

A

When one gene unequally shares genetic information with another gene

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28
Q

What do HLA-DM and HLA-DO do?

A

Regulate peptide loading in the phagolysosome

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29
Q

What are the two mechanisms that generate diversity in MHC molecules?

A
  1. MHC gene families contain multiple chain genes

2. Genetic polymorphisms

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30
Q

What happens once the MHC Class 2 molecule reaches the vesicle?

A

The invariant chain is cleaved, leaving behind the CLIP fragment that still prevents peptide binding

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31
Q

What do T cell receptors recognize?

A

Peptide antigens that are presented by MHC

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32
Q

When TCR binds, what does it make contact with?

A

Both the peptide and the MHC molecule

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33
Q

What is cross presentation?

A

When MHC Class 1 molecules present extracellular antigens

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34
Q

Where do the hypervariable regions of TCRs occur?

A

In the loops between the Ig domains

35
Q

What are the two types of diversity that contribute to differences in the TCR alpha and beta chains?

A

Combinatorial diversity and junctional diversity

36
Q

Which MHC class do CD4+ T cells interact with?

A

MHC Class 2

37
Q

What is the role of the invariant chain?

A

To block the binding of peptides to the MHC Class 2 molecule while it is still in the ER and to deliver the Class 2 molecule to the appropriate vesicles for peptide binding

38
Q

How is CLIP removed so that MHC Class 2 molecules can bind peptides?

A

Via the action of HLA-DM

39
Q

What are gamma-delta T cells?

A

T cells that express a gamma:delta heterodimer

40
Q

What is the immunoproteosome?

A

A special form of the proteosome for MHC Class 1, which is induced by Ifn-gamma

41
Q

What are the two types of MHC?

A

MHC Class 1 and MHC Class 2

42
Q

What is interallelic conversion?

A

When two alleles of the same gene exchange genetic information equally

43
Q

What are the different HLA Class 1 isotypes?

A

HLA-A, HLA-B, HLA-C, HLA-E, HLA-F, HLA-G

44
Q

What is the combination of allotypes that forms an MHC molecule called?

A

Isoform

45
Q

Why is it important that MHC molecules are polymorphic?

A

Being polymorphic provides MHC molecules with degenerate binding specificity, which allows them to bind a wide variety of peptides

46
Q

What are alloreactive T cells?

A

T cells that will recognize self-peptides presented by allogenic MHC

47
Q

What is antigen presentation?

A

When MHC displays a peptide on the cell surface

48
Q

What are the specifics of the MHC Class 2 binding pocket?

A

Binds with the side chains of peptides, and thus can bind to larger peptides than MHC Class 1

49
Q

What are the different HLA Class 2 isotypes?

A

HLA-DM, HLA-DO, HLA-DP, HLA-DQ, HLA-DR

50
Q

What is MHC restriction?

A

The requirement that T cells must recognize both the peptide and the specific MHC structure in order to be activated

51
Q

What is balancing selection?

A

The type of selection that acts to maintain MHC diversity by selecting for heterozygotes with haplotypes that minimally overlap

52
Q

What is an alloreaction?

A

When a transplanted organ presents self-peptides complexed with allogenic MHC, leading to rejection

53
Q

What do alloantibodies do?

A

Attack transplanted tissues in a woman if they have the same MHC as a man who fathered a previous pregnancy

54
Q

What is ERAP?

A

A peptidase that shortens peptides so that they fit into the MHC Class 1 molecule

55
Q

What part of MHC Class 2 does CD4 bind to?

A

The beta-2 domain

56
Q

What is directional selection caused by?

A

An epidemic disease

57
Q

What are alpha-beta T cells?

A

T cells that express an alpha:beta heterodimer

58
Q

What is the function of cytotoxic T cells?

A

To kill infected cells

59
Q

How does TCR interact with antigen?

A

Via cell-to-cell interactions

60
Q

What is the role of calnexin?

A

To stabilize the Class 1 heavy chain until Beta-2 microglobulin binds

61
Q

What forms the antigen binding domain of the TCR?

A

The variable regions of the TCR alpha and TCR beta chains

62
Q

What is the MHC Class 1 molecule composed of?

A

An MHC heavy chain (with domains alpha-1, alpha-2, alpha-3, and a transmembrane domain) and Beta-2 microglobulin

63
Q

What molecules form the peptide-loading complex?

A

Class 1 heterodimer, calreticulin, tapasin, TAP, ERp57, and PDI

64
Q

Where do Class 2 peptides bind?

A

In vesicles known as the MHC Class 2 compartment

65
Q

What part of MHC Class 1 does CD8 bind to?

A

The alpha-3 domain

66
Q

What do HLA-A, HLA-B, and HLA-C do?

A

Present peptides to CD8+ T cells and NK cells

67
Q

How can APCs be activated, if not infected by the virus itself?

A

By phagocytosing infected dead cells

68
Q

Why is it important that the cell is compartmentalized?

A

Peptides derived from intracellular pathogens (MHC Class 1) and are generated in a separate compartment than peptides derived from extracellular pathogens (MHC Class 2)

69
Q

Which Class 1 HLA remains intracellular with an unknown function?

A

HLA-F

70
Q

What kind of combinatorial diversity is observed in the TCR beta chain?

A

VDJ combination (like the heavy chain of antibodies)

71
Q

What is a unique feature of gamma-delta T cells?

A

They can bind antigens that are not presented by MHC

72
Q

What are the proteins encoded for by different alleles called?

A

Allotypes

73
Q

What is SCID?

A

Severe Combine Immunodeficiency - null mutations in RAG 1 and RAG 2 block TCR and immunoglobulin rearrangements, leading to a lack of B and T cells

74
Q

What is the MHC Class 2 molecule composed of?

A

An alpha chain and a beta chain, each containing a transmembrane domain, an Ig-like domain, and a peptide bonding domain

75
Q

What is the combination of MHC alleles on the chromosome called?

A

Haplotype

76
Q

How are new MHC genes generated?

A

Point mutations and recombination

77
Q

What is the CD3 complex?

A

Complex required for the proper transport of TCR that also relays signals into the cell once TCR binds its antigen

78
Q

Which MHC class do CD8+ T cells interact with?

A

MHC Class 1

79
Q

Why can allogenic MHC alloreactions be treated, but alloantibody alloreactions cannot?

A

There are drugs available that can inhibit T cell activation, but none that can inhibit the antibody response

80
Q

What is the function of helper T cells?

A

To help activate other effector cells

81
Q

What regions of a peptide do MHC molecules recognize?

A

The ends and the backbone

82
Q

Why are alpha-beta T cells and gamma-delta T cells mutually exclusive?

A

The delta chain locus is contained within the alpha chain locus, and gets deleted when the alpha chain is rearranged

83
Q

How are autologous MHC isoforms and allogenic MHC isoforms different?

A

The self MHC isoforms are referred to as autologous, while all others are considered allogenic

VBSC 211: The Immune System (10 decks)

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