Breakout #3

Question 1

Upon binding cytokine, how do cytokine receptors induce their signals?

Answer 1

JAK/STAT Pathway

Question 2

What is the function of JAK?

Answer 2

Bind to cytokine receptor and initiate cytokine receptor signaling pathway; also to phosphorylate STAT

Question 3

How are JAK proteins activated?

Answer 3

Tyrosine phosphorylation

Question 4

What is the function of STAT proteins?

Answer 4

After homo/heterodimerize with other STAT proteins, STAT will enter into the nucleus and act as a transaction factor

Question 5

In the Th1 Cell Differentiation pathway, what two cytokines work together to promote CD4+ T cells becoming Th1 cells?

Answer 5

IL-12 and IFN-gamma

Question 6

What happens after a naive T cell is activated through the TCR and CD28?

Answer 6

NFAT is activation and IFN-gamma binds to the IFN-gamma receptor

Question 7

Why is IFN-gamma binding to its receptor (IFN-gamma receptor) critical for initiation promotion of Th1 differentiation?

Answer 7

When IFN-gamma binds to its receptor, STAT1 is activated and increases T-bet

Question 8

What molecule does T-bet drive the production of?

Answer 8

T-bet drives IFN-gamma production

Question 9

How is the feedback loop of IFN-gamma binding to the IFN-gamma receptor augmented?

Answer 9

The feedback loop of IFN-gamma binding to IFN-gamma receptor is augmented by IL-12 binding to the IL-12 receptor to activate STAT4

Question 10

What molecules work together as transcription factors to augment T-bet to sufficient levels to permanently establish Th1 differentiation?

Answer 10

STAT4 and STAT1

Question 11

What is the master-regulator of Th1 cell differentiation?

Answer 11

T-bet

Question 12

What activates NFAT in Th1 cell differentiation?

Answer 12

Antigen (e.g pathogen) binding to TCR

Question 13

What two cells secrete IFN-gamma, which stimulates IFN-gamma receptor (thereby: inducing STAT1)?

Answer 13

APC and NK cells

Question 14

Although low levels of T-bet significantly increases levels of IFN-gamma transcription, what is required for commitment to Th1 phenotype?

Answer 14

High levels of T-bet are required for commitment to Th1 phenotype because it allows for:
a) shutting down IL-4 gene expression
b) alterations to the IFN-gamma promoter

Question 15

What is the master regulator of Th2 cell differentiation?

Answer 15

GATA-3

Question 16

How is NFAT activated in Th2 cell differentiation?

Answer 16

Naive T cells are activated via TCR and CD28

Question 17

If activated CD4+ T cell is activated in the presence of IL-4, binding of IL-4 to its receptor will induce what?

Answer 17

Phosphorylation of STAT6

Question 18

What induces the expression of GATA-3 (Th2 master regulator)?

Answer 18

STAT6 translocating into the nucleus

Question 19

How does GATA-3 function?

Answer 19

Binds to promoters of cytokines (IL-4, 5, and 6) and directly shuts down IFN-gamma gene expression

Question 20

What is ultimately responsible for permanently determine cytokine phenotype of Th cells?

Answer 20

Epigenetic modification of the chromosome

Question 21

What molecules associate with proteins that modify chromatin structure?

Answer 21

T-bet (Th1) and GATA-3

Question 22

True or False: The cytokine genes in a CD4+ T cell can be altered in a permanently open or closed state

Answer 22

True

Question 23

How does removing methylation from DNA affect accessibility of DNA to TF’s

Answer 23

Removing CH3 groups allows DNA to repel each other, increased accessibility to transcription factors

Question 24

How does acetylation of histones affect accessibility of transcription factors to DNA?

Answer 24

Acetylation increase accessibility of transcription factors to DNA

Question 25

What two molecules direct the localization of histone acetylases and demethylating enzymes to the Th1 and Th2 promoters?

Answer 25

T-bet and GATA-3

Question 26

In Th1 cells
- IFN-gamma promoter:
- IL-4 promoter:

In Th2 cells
- IL-4 promoter:
- IFN-gamma promoter:

Answer 26

In Th1 cells
- IFN-gamma promoter: demethylated + acetylated = open
- IL-4 promoter: methylated + deacetylated = closed

In Th2 cells
- IL-4 promoter: demethylated + acetylated = open
- IFN-gamma promoter: methylated + deacetylated = closed