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VBSC 211: The Immune System > Exam 6: Chapter 8 > Flashcards

Exam 6: Chapter 8 Flashcards

1
Q

What type of cell is needed to activate a CD8+ T cell?

A

An activated dendritic cell (and sometimes an activated CD4+ T cell)

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2
Q

What makes up the synapse attachment between CD8+ cells and their target cells?

A

The inner TCR:peptide/MHC, a secretory channel, an integrin binding area, and an outer region of bigger interacting molecules

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3
Q

What are the different types of effector T cells?

A

TH1, TH17, TH2, TFH, and Treg cells

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4
Q

What happens if ONLY the specific signal for T cell activation is present?

A

The T cell will be rendered anergic

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5
Q

What is the Fas ligand?

A

A ligand present on CD8+ T cells that binds to Fas receptors on target cells and signals for apoptosis to occur

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6
Q

What are the different pathways via which dendritic cells present antigens to T cells?

A

Receptor-mediated endocytosis, macropinocytosis, viral infection, cross-presentation, transfer from infected cell to resident cell

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7
Q

How do T cells know to home to secondary lymphoid organs?

A
  1. T cells have adhesion molecules on their surfaces
  2. The HEV has specialized adhesion molecules that interact with T cells
  3. T cells are also attracted by chemokines
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8
Q

What happens if a naïve T cell fails to find its antigen?

A

It will leave via the efferent lymphatic vessel

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9
Q

What are the two types of cells that take up antigens and process them for T cells?

A

Dendritic cells and macrophages

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10
Q

What is the function of TFH cells?

A

To activate B cell maturation

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11
Q

What happens if ONLY the co-stimulatory signal for T cell activation is present?

A

There is no effect on the cell

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12
Q

Where do dendritic cells reside within the secondary lymphoid organs?

A

The T cell area

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13
Q

How does a T cell know when it has bound a specific peptide/MHC complex?

A
  1. T cells sense the interaction of peptide/MHC via a TLR
  2. The TCR sends a signal to the cell; typically via protein phosphorylation of tyrosine residues
  3. Tyrosine phosphorylation changes the function of proteins or recruits more proteins to the TCR to be phosphorylated
  4. Protein phosphorylation leads to the activation of other signaling pathways
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14
Q

What is the function of Treg cells?

A

To suppress the other effector T cells

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15
Q

Where do antigens concentrate, thus making T cell recognition easier?

A

In the draining lymph node

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16
Q

What is the importance of the Ras-Map kinase pathway?

A

It leads to the activation of transcription factor AP-1. Co-stimulation through CD28 maintains Lck activation and helps in the activation of AP-1

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17
Q

What are macrophages?

A

Resident cells that remain in the infected tissue

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18
Q

Why is the pathway that activates Protein Kinase C important?

A

This pathway leads to the activation of transcription factor NFkB

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19
Q

What is the role of granulysin?

A

To break down the target cell membrane

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20
Q

Where do macrophages reside within the secondary lymphoid organs?

A

Both the T and B cell areas

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21
Q

What causes the delay in the adaptive immune response?

A

The time it takes to activate and differentiate effector T cells

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22
Q

How do T cells enter the lymph node?

A

Via the high endothelial venule

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23
Q

What are the key kinases associated with the TCR complex?

A

Lck and Zap-70

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24
Q

How does the synapse form?

A

A CD8+ T cell and a target cell collide and undergo nonspecific adhesion. Specific recognition then redistributes cytoplasmic and cytoskeleton components of the cell. Lytic granules are localized and released into the synapse between the two cells

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25
Q

What is the function of TH2 cells?

A

Activate the response against parasites

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26
Q

What are the two components of the AP-1 transcription factor?

A

Fos and Jun

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27
Q

How do lymphocytes enter the lymph node?

A

The lymphocyte begins a rolling interaction. LFA-1 activated by chemokines then binds tightly to ICAM-1, and the lymphocyte enters the lymph node via diapedesis

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28
Q

What signaling molecule tells a naïve T cell to leave the lymph node?

A

Sphingosine-1-phosphate

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29
Q

What are the properties of activated macrophages?

A
  1. Increased fusion of phagosomes with the lysosome
  2. Increased production of microbicidal molecules
  3. Increased expression of B7 and MHC class II
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30
Q

What is the role of VLA-4?

A

To allow T cells to interact with endothelial cells in inflamed, infected tissues

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31
Q

What co-stimulatory receptor is expressed by T cells?

A

CD28

32
Q

What is the function of TH1 cells?

A

Activate macrophages

33
Q

What two signals are required to activate a T cell?

A
  1. Interaction between TCR/co-receptor and peptide/MHC

2. A co-stimulatory signal sent only by APCs

34
Q

What does interferon gamma do?

A
  1. Inhibits viral replication
  2. Increases MHC class I expression
  3. Activates macrophages at the site of infection to remove dead cells
35
Q

What is CTLA-4?

A

A second receptor that binds co-stimulatory molecules but serves to turn off T cell activation

36
Q

Why is it good to have T cell activation regulated by CTLA-4?

A
  1. Ensures a polyclonal T cell response

2. Keeps T cell response from overreacting and damaging healthy cells/tissues

37
Q

How do lytic granules kill infected cells?

A

By releasing enzymes that induce apoptosis

38
Q

How are T cells able to “sample” the peptide/MHC complexes on the antigen-presenting cells?

A

T cell adhesion molecules interact with complementary molecules on dendritic cells and macrophages

39
Q

What signal mediates cytokine responses?

A

STAT

40
Q

What upregulates B7 expression?

A

The danger signal

41
Q

How are co-stimulatory signals regulated?

A

They are only expressed when induced by infection

42
Q

What is the function of CD8+ T cells?

A

To kill cells infected with viruses and intracellular pathogens that antibodies cannot access

43
Q

Which type of T cell is harder to activate and why?

A

CD8+ cells, because these cells differentiate into cytotoxic T cells that can kill other cells

44
Q

What is cognate interaction?

A

The idea that TFH dependent help only occurs when B and T cells recognize the same antigen, but not necessarily the same epitope of that antigen

45
Q

What are ITAMs?

A

Conserved sequences with two tyrosine residues that are present in the CD3 complex and are phosphorylated by kinases

46
Q

Do the TCR and the associated CD3 complex have the ability to phosphorylate?

A

No, kinases must be recruited

47
Q

Why are so many phosphorylation events required for T-cell activation?

A

T cells use the duration of the TCR-peptide/MHC interaction to determine if the interaction is a specific one; longer interactions allow for more events to occur and for full signaling to activate

48
Q

What is adjuvant?

A

A mixture of bacterial products found in vaccines that activate the expression of MHC class II and co-stimulatory molecules

49
Q

Which kinase phosphorylates the ITAMs?

A

Lck

50
Q

How is sphingosine-1-phosphate turned off?

A

By activated T cells

51
Q

Why are transcription factors NFAT, NFkB, and AP-1 important?

A

All three are necessary to form effector T cells

52
Q

Why is the co-stimulatory signal necessary for T cell activation?

A

It ensures that only APCs can activate T cells

53
Q

What are dendritic cells?

A

Cells that are highly migratory, present in the periphery, and act as sensors for infection

54
Q

What are regulatory T cells?

A

Antigen specific T cells that act to suppress auto-immune reactions

55
Q

Why is it important that CD8+ cells kill via apoptosis and NOT necrosis?

A

Death by necrosis would lead to the leakage of pathogens into the extracellular space

56
Q

How do dendritic cells become mature and activated?

A

By taking up antigens and processing them for presentation

57
Q

What are granzymes?

A

Proteases that initiate apoptosis

58
Q

How is the TH1 response regulated?

A
  1. TH2 cytokines inhibit the TH1 response

2. TH1 T cells must maintain contact with TCR:peptide/MHC in order to produce interferon gamma

59
Q

What is the function of TH17 cells?

A

Enhance neutrophil response

60
Q

What is the importance of the pathway that induces Ca2+ from outside of the cell into the cell?

A

The increase of Ca2+ inside the cell activates the transcription factor NFAT

61
Q

What is the role of CD45RA and CD45RO?

A

To dephosphorylate an inhibitory site on Lck

62
Q

How do TFH cells activate B cells?

A

TFH cells recognize peptide/MHC presented by B cells, form a synapse, and secrete cytokines that activate B cell differentiation

63
Q

What are the two functions of chemokines that attract T cells?

A
  1. To mark the HEV and attract T cells

2. To send a signal to the T cell that activates the ability of integrins to bind ICAMS

64
Q

What two signals are required for macrophage activation?

A

CD40 ligand and Interferon gamma

65
Q

What type of receptors are involved in the activation of dendritic cells?

A

Toll-like receptors

66
Q

What co-stimulatory molecule is expressed by APCs?

A

B7

67
Q

Where do adaptive immune responses occur?

A

In secondary lymphoid organs

68
Q

What mediates the interaction between T cells and endothelial cells?

A

Interactions between selectins on the T cells and mucin-like vascular addressins on the endothelial cells

69
Q

What is the role of perforin?

A

To make holes in the target cell membrane

70
Q

How do NFAT, NFkB, and AP-1 induce proliferation of activated T cells?

A

By inducing the expression of IL-2, a cytokine which stimulates T cells to proliferate

71
Q

What are the properties of effector T cells?

A
  1. Detach from the APCs
  2. Effector functions are induced by specific TCR:peptide/MHC interaction
  3. Do not require co-stimulation
  4. Increase expression of adhesion molecules that will allow them to interact with target cells
72
Q

What happens if a pathogen can resist activated macrophages?

A

The immune system walls off these infected cells and forms a granuloma

73
Q

What two immunosuppressant drugs target NFAT activation?

A

Cyclosporin A and FK506

74
Q

What happens after Lck phosphorylates the ITAMs?

A

The phosphorylated ITAMs serve as bonding sites for Zap-70. Lck also phosphorylates Zap-70, increasing its kinase activity

75
Q

Why are lytic granules precisely localized?

A

To prevent the killing of bystander cells

VBSC 211: The Immune System (10 decks)

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