Antigen Presenting Cells/T Cell Activation

Question 1

T cell activation occurs exclusively in ____

Answer 1

secondary lymphoid tissue (this is the only place where there’s enough contact between APCs and T cells)

Question 2

Two signals required for T cell activation

Answer 2

1. binding of TCR to it’s cognate determinant

binding of CD28 and B7 expressed by antigen presenting cells

Question 3

Naive T cells can only be activated by ____

Answer 3

antigen binding cells (dendritic cells, macrophages, and B cells)

Question 4

L-selectins

Answer 4

on the surface of naive T cells, interacts with addressins (CD34 and glycam-1) so that the T cells can diapedese into HEVs

Question 5

glycam-1 and CD34

Answer 5

addressins on the surface of HEVs, bind L-selectins on T cells
glycam-1 also known as sulfonate sialyl-lewis

Question 6

LFA-1

Answer 6

adhesion molecule expressed on naive and effector T cells (higher concentration of effectors)
binds iCAM on HEV’s
also binds iCAM on antigen presenting cells to allow close interaction between the T cells and APCs

Question 7

VLA-4

Answer 7

adhesion molecule expressed on activated T cells, binds VCAM-1 in order to enter inflammatory tissues

Question 8

B7 co-stimulator

Answer 8

expressed on the surface of APCs after encounter with a pathogen, needed for T cell activation, interacts with CD28

Question 9

Dendritic cells only express B7 in _____

Answer 9

secondary lymphoid tissues

Question 10

Macrophages and B cells express B7 in an _____

Answer 10

inducible manner

Question 11

Dendritic cells are most important APCs for ___

Answer 11

presentation of viral determinants

Question 12

Macrophages are most important APC’s for ____

Answer 12

presentation of bacterial deteminants

Question 13

langerhans cells

Answer 13

immature dendrites

Question 14

Where does T cell activation always occur?

Answer 14

secondary lymphoid tissues

Question 15

T cell activation results in

Answer 15

1. clonal expansion
2. upregulation of IL-2
3. upregulation of high affinity form of IL-2 receptor (CD25)

Question 16

IL-2

Answer 16

autocrine growth factor that drives proliferation and activation of T cells

Question 17

CD25

Answer 17

alpha chain of IL-2 receptor, important for high affinity form
(beta and gamma important for lower affinity receptor)

Question 18

What happens to a T cell if there is no B7 activation?

Answer 18

becomes anergic and is inactivated

Question 19

peripheral tolerance

Answer 19

because APCs only express B7 when they recognize a pathogen, and because without B7 co-stimulation a T cell undergoes apoptosis, if a naive T cell binds a MHC:self peptide complex it will be inactivated.

Question 20

When are autoimmune disease most often initiated?

Answer 20

during infection with pathogen

Question 21

3 ways for CD8 T cells to be activated

Answer 21

1. dendritic APC’s express enough B7 to activate CD8 cells without any help
2. macrophage- activate here CD4 cells which activate the APCs to produce more B7 and activate the CD8 T cell
3. B cells or macrophage- activate CD4 to make IL-2 and CD8 cell to express the IL-2 receptor. IL-2 secreted by CD4 binds CD8 receptors-drives proliferation and activation

Question 22

effector T cell

Answer 22

T cell that is fully differentiated to perform it’s effector function

Question 23

Do effector T cells require B7 co-activation?

Answer 23

No

Question 24

CD8 T cells

Answer 24

cytotoxic T cells, most suitable T cell for limiting virus infection

Question 25

CD4 T cells

Answer 25

produce cytokines and cheekiness that activate other cell types

Question 26

Th1 T cells

Answer 26

important for clearance of intracellular infections, supply second signals of B cell activation, activate macrophages

Question 27

Th2 cells

Answer 27

important for clearance of extracellular infections, supply second signals of B cell activation, down-regulate macrophage activity

Question 28

Two primary Th1 cytokines

Answer 28

IL-2-helps promote activation of CD8 cells | IFN-gamma-activate macrophages

Question 29

Two primary Th2 cytokines

Answer 29

``` IL-4-initiates class switching to IgA Il-5initiates class switching to IgE ```

Question 30

Cytokines that promotes Th0>>>Th1

Answer 30

IL-12 and IFN-gamma

Question 31

cytokines that promote Th0>>>Th2

Answer 31

IL-4, 5, 6, 10 (4 most important, from a subset of NK cells)

Question 32

NK T cells

Answer 32

produce IL-4 promoting differentiation of Th0>>>Th2

Question 33

Treg cells

Answer 33

if activated in the secondary lymphoid tissue by binding self-peptides they produce IL-10 and TGF-beta (anti-inflammatory) which down-regulates activation of other surrounding T cells in order to prevent autoimmune response

Question 34

FoxP3

Answer 34

transcription factor that drives expression of IL-10 and TGF-beta

Question 35

T-bet

Answer 35

transcription factor that drives expression of Th1 cytokines (IL-2 and IFN-gamma)

Question 36

Gata-3

Answer 36

transcription factor that drives expression of Th2 cytokines (IL-4.5)

Question 37

Th17

Answer 37

produces IL-17-neutrophil chemotractant IL-22-antimicrobial peptide production by epithelial cells

Question 38

E-selectin upregulation stimulated by

Answer 38

TNF-alpha and IL-1, allows leukocytes like neutrophils to diapedese into inflammatory tissue

Question 39

DC-CK

Answer 39

chemotactic signal on dendritic cells that acts as a chemotactant for naive T cells

Question 40

T/F B7 binding CD28 in the absence of the first activation signal has no response

Answer 40

True

Question 41

T/F Macrophages produce IL12 which stimulates NK cells to produce IFN-gamma which then activates Th0>>Th1

Answer 41

true