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Immunology Test 1 > 6 T Cell Antigen Recognition and Activation > Flashcards

6 T Cell Antigen Recognition and Activation Flashcards

1
Q

What are T cells activated by?

A

APC sampling

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2
Q

What is the overview of T cell activation?

A
  1. Adhesion to APCs
  2. Activation Signals
  3. T cell differentiation
  4. T cell proliferation
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3
Q

What are the first T cell molecules to bind to APCs?

A

LFA1 to ICAM1

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4
Q

What does LFA1 binding to ICAM1 allow?

A

TCR/CD4 and 8 binding to MHC

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5
Q

What sends signals to tighten the LFA1/ICAM1 binding?

A

TCR/CD4/8 binding to MHC

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6
Q

What is the signal cascade from TCR/MHC complexes?

A

CD3!!!!

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7
Q

What is the first signal of activation?

A

CD3

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8
Q

What is the second (costimulating) signal of T cell activation?

A

B7 binding to CD28

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9
Q

If B7 comes before TCR/MHC binding and CD3, what happens?

A

Nothing, cell does not activated

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10
Q

What two signals does a T cell need to activate?

A

CD3 transduction

B7 costimulation

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11
Q

What happens to the T cell if the B7 does not bind after CD3 signal goes out?

A

Apoptosis

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12
Q

What three signal pairings do T cells need to recognize an antigen?

A

MHC/TCR
CD28/B7
CD3

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13
Q

What one signal pair does a T cell need to proliferate?

A

IL2 and IL2Receptor

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14
Q

What is the difference between naive and mature T cell IL2R?

A

Mature IL2R has a higher affinity

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15
Q

How does the body create tolerance for some activated self-recognizing T cells that escape the thymus negative selection?

A

B7 is required for costimulation and needs ot be induced in APCs during infection
Thus, B7 levels remain low during health and CD8s do not kill everything even if MHCs are presented.

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16
Q

What signal caused T cell death if it is absent after MHC recognition?

A

B7

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17
Q

Why do autoimmune reactions occur during infections?

A

Macrophages present self-peptides and antigen peptides to T cells

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18
Q

When is the only time T cells should proliferate?

A

Infection

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19
Q

Which type of T cell requires more signaling?

A

CD8 Cytotoxic

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20
Q

What three ways can a T cell be activated?

A
  1. DCs activate T cell
  2. APC presents. T cell activates APC. APC activates T cell.
  3. APC activates CD4 to make IL2 and CD8 to make IL2R. CD4 activates CD8
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21
Q

What is different about a fully differentiated T cell?

A
  1. no Costimulator required

2. Adhesion Molecules are different

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22
Q

What are the three main types of armed effector T cells?

A

CD8

CD4: Th1 and Th2

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23
Q

What CD8 enzyme makes holes in membranes?

A

Perforin

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24
Q

What CD8 enxyme enters pores in membranes to cause apoptosis?

A

Granzymes

Granylysin

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25
Q

What signal cascade do granzymes and granulysin use?

A

Caspase

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26
Q

What are the main CD8 cytokines?

A

IFN-y

Lymphotoxin

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27
Q

What is the main function of CD4 Helper T cells?

A

To induce antibody class switching in B cells

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28
Q

What actives CD40 on macrophages?

A

IFNy

29
Q

What is special about Th1 CD4 T cells?

A

Activate Macrophages in addition to B cells

30
Q

What is notable about Th2 CD4 T cells?

A

Activate B cells only

31
Q

What makes macrophages better killers?

A

CD40 binding of T cell IFNy made by Th1 cells

32
Q

What signals Th1 formation from CD4 T helper zero cells?

A

IL12, IFNy

33
Q

Why would Th1 cells need to be formed?

A

Viral infection: T cells needed to order B cells to make Viral based antibodies

34
Q

What signals Th2 cells from CD4 Helper Zero cells?

A

IL4, IL5 (makes GATA-3 transcription factor)

35
Q

Why would CD4 helper T cells form?

A

In response to an extracellular Infection, since they respond to MHC class II bound peptides from the endogenous antigen presentation pathway

36
Q

Why would CD8 cytotoxic T cells form?

A

In response to an intracellular (viral) infection, since they respond to the MHC class I peptide produced from the cytosolic antigen pathway of proteosomic cleavage.

37
Q

What are all helper T cells originally?

A

T helper zero cells

38
Q

What do T Regulatory cells express that is unique?

A

FoxP3 transcription factor that increases IL10 and TGF-B to decrease cell response to infection

39
Q

What do T Regulator cells do?

A

Decrease CD4 and CD8 response to infection

40
Q

What two big factors determine Helper T cell class?

A

Cytokine

Antigen Concentration

41
Q

What does high concentration of antigen likely mean?

A

Intracellular (viral) infection

42
Q

What does high concentration of antigen promote?

A

Th1 cells

43
Q

What does low concentration of antigen mean?

A

Extracellular (bacterial?) infection

44
Q

What does low concentation of antigen promote?

A

Th2 cells

45
Q

Th1 cells are best at producing cytokines for handling what type of infection?

A

Intracellular

46
Q

Th2 cells are best at producing cytokines for handling what type of infection?

A

Extracellular

47
Q

What are Natural Killer cells?

A

Cells that kill viral infected cells

Cells that make Interfuron-Gamma to induce Th1 production and Interleukin 4 to induce Th2

48
Q

What NK signal makes Th1?

A

IFN-y

49
Q

What NK signal makes Th2?

A

IL-4

50
Q

Viruses cause Dendritic Cells to make what to turn up NK cell IFN-y secretion?

A

IL-12

51
Q

What do NK cells secrete to induce Th2 cells?

A

IL-4 in response to worms

52
Q

Where are T Helper 17 cells found?

A

Mucosal epithelium inflammation

53
Q

What do T Helper 17 produce to activate neutrophils?

A

IL 17

54
Q

IL 17 activates what?

A

Neutrophils

55
Q

What downregulates Th2 development?

A

Th1

56
Q

What downregulates Th1 development?

A

Th2

57
Q

What downregulated both Th1 and Th2 development?

A

T Reg cells

58
Q

Adaptive responses never happen where?

A

At the site of infection

59
Q

Adaptive responses only happen where?

A

Secondary Lymph

60
Q

Where to naive T cells live?

A

T cell zones of secondary lymph

61
Q

B7 binds to what receptor on T cells?

A

CD28

62
Q

B cells are unique as APCs because they bind what type of antigen?

A

Soluble antigen

63
Q

If a T cell is not activated by a DC, what else must also likely be present?

A

Both CD8 and CD4 cell types

64
Q

What do activated T cells express that keeps them at the infection site?

A

VLA4 adhesion molecules

65
Q

What do activated T cells not express that keeps them from recirculating into the lymph?

A

L Selectin

66
Q

What signal downregulates Th2 cells?

A

IFN-y

67
Q

What produces IFN-y to downregulate Th2 cells?

A

NK and Th1

68
Q

The absence of FoxP3 gene leads to what disease?

A

Autoimmune IPEX syndrome

Immunology Test 1 (12 decks)

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