Activation Of T Lymphocytes

Question 1

Activated T cells differentiate into effector cells. What are the two fates of the effector cells?

Answer 1

Remain in the lymphoid organs to help B lymphocytes

Migrate to sites of infection to help activate macrophages.

Question 2

What cytokine is secreted as Ags are recognized by T cells?

Answer 2

IL-2.

This results in clonal expansion as a result of proliferation and differentiation of the T cells into effector or memory cells.

Question 3

How do effector CD4 T cells respond to Ags?

Answer 3

They produce cytokines that have several actions, such as the recruitment and activation of leukocytes and activation of B cells.

Question 4

What is the function of effector CD8 CTLs?

Answer 4

They kill infected and altered host cells.

Question 5

What three things ocur when Ag recognition and other activating stimuli induce responses in T cells?

Answer 5

Secretion of cytokines

Proliferation (clonal expansion)

Differentiation into effector and memory cells.

Question 6

What are the functions of effector T cells?

Answer 6

To perform functions that are responsible for the elimination of microbes, and in disease states, for tissue damage.

Question 7

What occurs to T cell responses after the Ag is eliminated?

Answer 7

T cell responses decline.

Question 8

What are the three signals needed for the proliferation of T lymphocytes and their differentiation into effector and memory cells?

Answer 8

Ag recognition

Costimulation

Cytokines

Question 9

What is required for the activation of naive T cells?

Answer 9

Ag presented by DCs.

The effector T cells can recognize Ags presented by tissue macrophages and B cells.

Question 10

What results from the activation of PLC1?

Answer 10

The production of IP3 and DAG.

Question 11

What occurs from the production of IP3?

Answer 11

Increases of cytosolic free calcium

Question 12

What does T cell receptor signaling overall result in?

Answer 12

The activation of Ras and MAPK, which activate transcription factors such as NFAT and NF-KB.

Question 13

What do superantigens bind to?

Answer 13

To MHC class II molecules and the V region of the beta subunit of the TCR.

Question 14

What occurs to T cells upon superantigen acitvation?

Answer 14

T cells produce massive amounts of cytokines which may lead to shock.

Question 15

How do superantigens (SAgs) bind to TCR?

Answer 15

Via the variable region of the beta chain.

Question 16

When activated APCs are present, what is there increased expression of?

Answer 16

Costimulators, as well as the secretion of cytokine IL-2

Question 17

What are the three signals required in costimulation in T cell activation?

Answer 17

Ag recognition

Inflammation and activation of costimulators (B7)

Production of cytokiens of IL-12

Question 18

What results from increased secretion of IL-2 or expression of IL-2R?

Answer 18

Cell proliferation

Question 19

What is the best characterized costimulatory pathway in T cell activation?

Answer 19

T cell surface receptor CD 28, which binds co stimulatory molecules B7-1 and B7-2 (CD80 and CD86).

These are expressed on activated APCs

Question 20

What is the function of B7 costimulators?

Answer 20

It ensures that T lymphocyte responses are initiated only wheen needed.

Question 21

What is the result of CD28 and Ag recognition?

Answer 21

The survival, proliferation and differentiation of specific T cells.

Question 22

How is T cell activation influenced?

Answer 22

It is influenced by a balance between engagement of activating and inhibitory receptors of the CD28 family.

Question 23

What is the result of CD28 and B7-1?

Answer 23

Costimulationof naive T cells; generation of regulatory T cells.

Question 24

What is the function of B7-2 and CTLA-4?

Answer 24

Negative regulation of immune responses; self-tolerance

Question 25

Where are B7-1 and B7-2 found?

Answer 25

DCs, macrophages and B cells.

Question 26

Where are CD28, CTLA-4, iCOS and PD-1 found?

Answer 26

On T cells

Question 27

What is the function of iCOS?

Answer 27

Costimulatio nof effector and regulatory T cells; generation of follicular helper T cells.

Question 28

What is the function of CD274 and CD273 & PD-1?

Answer 28

Negative regulation of T cells.

Question 29

When is CTLA4-mediated immune checkpoint induced in naive T cells?

Answer 29

At the time of their initial response to Ag.

Question 30

True or false: naive memory T cells express high levels of cell surface CD28 but do not express CTLA4 which is stored in intracellular vesicles.

Answer 30

True

Question 31

After a TCR is triggered by an AG encounter, where is CTLA4 transported to?

Answer 31

The cell surface

Question 32

The stronger the stimulation through the TCR (and CD28), the ____ the amount of CTLA4 that is deposited on the T cell surface.

Answer 32

Greater. Therefore, CTLA4 functions as a signal dampener to maintain a consistent level of T cell activation.

Question 33

What is the major role of the programmed cell death protein 1 (PD1 pathway)?

Answer 33

To regulate inflammatory responses in tissues by effector T cells recognizing Ag in peripheral tissues.

Question 34

What do activated T cells upregulate?

Answer 34

PD1

Question 35

What do inflammatory signals in the tissue induce?

Answer 35

The expression of PD1 ligands.

Question 36

What is the function of PD1L?

Answer 36

It downregulates the activity of T cells and thus limits collateral tissue damage in response to a microorganism infection in that tissue.

Question 37

What occur when there is excessive induction of PD1 on T cells?

Answer 37

It can induce an exhaused or anergic state in T cells.

Question 38

What is the primary function of IL-2?

Answer 38

It is a survival signal.

Question 39

What are functions of IL-2?

Answer 39

Autocrine growth factor for CD4+ and CD8+ T cells Potentiates cytotoxicity of NK cells and CD8+ T cells. Costimulates T cells to produce IL-4, IL-5, and IFN-gamma Promotes the development of regulatory T cells. Induces an autocrine activation-induced death in T cells.

Question 40

What cytokine induces the anti-apoptotic protein Bcl-2?

Answer 40

Il-2

Question 41

True or false: no other cytokine can replace IL-2 for the maintenance of functional Treg cells.

Answer 41

True

Question 42

What is another term for IL-2R alpha?

Answer 42

CD25

Question 43

What is the function of CD69?

Answer 43

It binds to and reduces surface expression of S1PR1. As a result, activated T cells are retained in the LNs long enough to receive the signals that initiate their proliferation and differentiation into effector and memory cells.

Question 44

When is a period in which CD6 expression decreases?

Answer 44

After cel division.

Question 45

What is the result of the expression of S1PR1?

Answer 45

Effector and memory cells can exit lymphoid organs.

Question 46

What does CD28 bind to on an APC?

Answer 46

A costimulator (B7) This causes the expression of IL-2R alpha

Question 47

What does Ag recognition induce?

Answer 47

The expression of CD40 ligand on the activated T cells.

Question 48

What is the function of CD40L?

Answer 48

It enables activated T cells to help DCs, macrophages and B cells to become better APCs.

Question 49

What is the function of CTLA-4?

Answer 49

It functions as an inhibitor of T cell activation and thus as a regulator of the response.

Question 50

Elimination of Ag leads to __ of T cell response.

Answer 50

Contraction

Question 51

What occurs as levels of costimulation and IL-2 decrease?

Answer 51

The levels of anti-apoptotic proteins in the cells drop. IL-2 starvation triggers the mitochondrial pathway of apoptosis.

Question 52

What regulatory mechanisms contribute to the normal contraction of immune responses?

Answer 52

CTLA4 and PD-1 Apoptosis induced by TNFRI and Fas Treg cells

Question 53

According to the linear model of memory T cell differentiation:

Answer 53

Most effector cells die Some survivors develop into the memory cells.

Question 54

According to the branched differentiation model:

Answer 54

Effector and memory cells are alternative fates of activated T cells.

Question 55

How long to memory cells specific for Ags last?

Answer 55

Years or even a lifetime.

Question 56

What cells constitute the most abundant lymphocyte population in the body for the majority of a person's lifetime?

Answer 56

Memory T cells.

Question 57

Where do the vast majority of memory T cells reside?

Answer 57

In tissue sites, including lymphoid tissues, intestines, lungs and skin.

Question 58

What is the role of T-bet?

Answer 58

It drives the differentiation of effector cells in CD4+ T cells.

Question 59

What does Blimp-1 promote the generation of?

Answer 59

Memory cells

Question 60

What are three major properties of memory cells?

Answer 60

They can remain dormant without an Ag. They mount larger enhanced responses to Ag than do naive cells. The number of memory T cells specific for any Ag is greater than the number of naive cells specific for the same Ag

Question 61

True or false: memory cells are able to migrate to peripheral tissues and respond to Ag at the sites.

Answer 61

True

Question 62

Memory cells undergo slow ___ that may contribute to the long life span of the memory pool.

Answer 62

Self-renewing

Question 63

The maintenance of memory cells is dependent on ____ but does not require Ag presence.

Answer 63

Cytokines

Question 64

What cytokines induce the expression of anti-apoptotic proteins and stimulate low-level proliferation?

Answer 64

IL-7 and IL-15

Question 65

What three distinct phases to memory T cells pass through?

Answer 65

Memory generation Memory homeostasis Immunosenescence

Question 66

What are phenotypic markers for memory T cells?

Answer 66

IL-7R CD45 CD27

Question 67

What do central memory T cells express, and where do they home to?

Answer 67

They express CCR7 and L-selectin and home mainly to LNs, spleen and circulate in the blood.

Question 68

Where do effector memory T cells proliferate, and what do they produce?

Answer 68

IFN-gamma dn TNF or become cytotoxic.

Question 69

What are resident tissue memory T cells?

Answer 69

T cells that reside in epithelial barrier tissues at the interface between the host and the environment.

Question 70

What do resident tissue memory T cells produce?

Answer 70

IFN-gamma and TNF. They are specific for pathogens and other Ags that have been encountered previously through that barrier epithelium.

Question 71

When does activation of naive T cell occur in the lymph nodes?

Answer 71

Activation occurs if they encounter TCR specific Ags.