6 T Cell Antigen Recognition and Activation Flashcards Preview

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

Flashcards in 6 T Cell Antigen Recognition and Activation Deck (68):
1

What are T cells activated by?

APC sampling

2

What is the overview of T cell activation?

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

3

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

LFA1 to ICAM1

4

What does LFA1 binding to ICAM1 allow?

TCR/CD4 and 8 binding to MHC

5

What sends signals to tighten the LFA1/ICAM1 binding?

TCR/CD4/8 binding to MHC

6

What is the signal cascade from TCR/MHC complexes?

CD3!!!!

7

What is the first signal of activation?

CD3

8

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

B7 binding to CD28

9

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

Nothing, cell does not activated

10

What two signals does a T cell need to activate?

CD3 transduction
B7 costimulation

11

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

Apoptosis

12

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

MHC/TCR
CD28/B7
CD3

13

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

IL2 and IL2Receptor

14

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

Mature IL2R has a higher affinity

15

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

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.

16

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

B7

17

Why do autoimmune reactions occur during infections?

Macrophages present self-peptides and antigen peptides to T cells

18

When is the only time T cells should proliferate?

Infection

19

Which type of T cell requires more signaling?

CD8 Cytotoxic

20

What three ways can a T cell be activated?

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

21

What is different about a fully differentiated T cell?

1. no Costimulator required
2. Adhesion Molecules are different

22

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

CD8
CD4: Th1 and Th2

23

What CD8 enzyme makes holes in membranes?

Perforin

24

What CD8 enxyme enters pores in membranes to cause apoptosis?

Granzymes
Granylysin

25

What signal cascade do granzymes and granulysin use?

Caspase

26

What are the main CD8 cytokines?

IFN-y
Lymphotoxin

27

What is the main function of CD4 Helper T cells?

To induce antibody class switching in B cells

28

What actives CD40 on macrophages?

IFNy

29

What is special about Th1 CD4 T cells?

Activate Macrophages in addition to B cells

30

What is notable about Th2 CD4 T cells?

Activate B cells only

31

What makes macrophages better killers?

CD40 binding of T cell IFNy made by Th1 cells

32

What signals Th1 formation from CD4 T helper zero cells?

IL12, IFNy

33

Why would Th1 cells need to be formed?

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

34

What signals Th2 cells from CD4 Helper Zero cells?

IL4, IL5 (makes GATA-3 transcription factor)

35

Why would CD4 helper T cells form?

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

36

Why would CD8 cytotoxic T cells form?

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

What are all helper T cells originally?

T helper zero cells

38

What do T Regulatory cells express that is unique?

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

39

What do T Regulator cells do?

Decrease CD4 and CD8 response to infection

40

What two big factors determine Helper T cell class?

Cytokine
Antigen Concentration

41

What does high concentration of antigen likely mean?

Intracellular (viral) infection

42

What does high concentration of antigen promote?

Th1 cells

43

What does low concentration of antigen mean?

Extracellular (bacterial?) infection

44

What does low concentation of antigen promote?

Th2 cells

45

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

Intracellular

46

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

Extracellular

47

What are Natural Killer cells?

Cells that kill viral infected cells
Cells that make Interfuron-Gamma to induce Th1 production and Interleukin 4 to induce Th2

48

What NK signal makes Th1?

IFN-y

49

What NK signal makes Th2?

IL-4

50

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

IL-12

51

What do NK cells secrete to induce Th2 cells?

IL-4 in response to worms

52

Where are T Helper 17 cells found?

Mucosal epithelium inflammation

53

What do T Helper 17 produce to activate neutrophils?

IL 17

54

IL 17 activates what?

Neutrophils

55

What downregulates Th2 development?

Th1

56

What downregulates Th1 development?

Th2

57

What downregulated both Th1 and Th2 development?

T Reg cells

58

Adaptive responses never happen where?

At the site of infection

59

Adaptive responses only happen where?

Secondary Lymph

60

Where to naive T cells live?

T cell zones of secondary lymph

61

B7 binds to what receptor on T cells?

CD28

62

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

Soluble antigen

63

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

Both CD8 and CD4 cell types

64

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

VLA4 adhesion molecules

65

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

L Selectin

66

What signal downregulates Th2 cells?

IFN-y

67

What produces IFN-y to downregulate Th2 cells?

NK and Th1

68

The absence of FoxP3 gene leads to what disease?

Autoimmune IPEX syndrome