Effector functions of T cells

Question 1

Where are T cells produced?

Answer 1

Their progenitors are produced in the BM which then migrate and mature in the thymus via TCR recombination and tolerance selection. They leave the thymus as differentiated CD4 or CD8 cells searching for MHC.

Question 2

What determines a T cells function?

Answer 2

Must bind with high affinity to proliferate and differentiate. The type and duration of a cytokine profile signal determines the function.

Question 3

What are the subtypes of CD4 Th cells?

Answer 3

Th1
Th2
Th17
Treg

Question 4

What do CD4 Th cells respond to?

Answer 4

MCH II extracellularly in response to viruses, bacteria, protozoa, fungi, worms

Question 5

What do CD4 Th functions result in?

Answer 5

Complement cascade, phagocytosis and antibodies

Question 6

What do cytotoxic CD8 cells respond to?

Answer 6

Intracellular MCH I in response to viruses and protozoa

Question 7

What do cytotoxic CD8 functions result in?

Answer 7

NK and cytotoxic T cell activation

Question 8

What are the three signals needed for T cell differentiation?

Answer 8

1st - binding of TCR to DC with good affinity
2nd - sufficient costimulation = proliferation
3rd - Cytokines and DC surface molecules drive downstream pathways to upregulate a specific lineage of TF for specific interleukin production.

Question 9

What is the function of a CD8 T cell?

Answer 9

Activate macrophages for intracellular pathogen killing.
Contain cytotoxic granules of perforin and granzymes to mediate cell death.
Express Fas ligand to kill susceptible cells via apoptosis.

Question 10

What stimulates a CD8 T cell?

Answer 10

MHC I on DC, CD4 Th cell or high conc of IL-2

Question 11

What cytokines cause differentiation to Th1?

Answer 11

IL-12, IL-2 and their own effector cytokine IFNgamma

Question 12

What TF controls transcription of the cytokines released by Th1 and what are they?

Answer 12

Tbet - TNFgamma and IL-2

Question 13

What type of infections are Th1 cells important for and what immune cells do they activate?

Answer 13

Activate macrophages in response to intracellular bacteria in vacuoles. Involved in delayed hypersensitivity reactions and cytotoxic T cell activation.

Question 14

What cytokines cause differentiation to Th2?

Answer 14

IL-4

Question 15

What cytokines are released by Th2 and what TF controls it?

Answer 15

GATA-3 = IL-3, IL-4, IL-5, IL-10, IL-13

Question 16

What type of infections are Th2 cells important for and what immune cells do they activate?

Answer 16

Promote B cell activation through class switching to IgE. Involved in allergic reactions and helminth infections. Induce rise in IgE and eosinophil levels.

Question 17

What cytokines cause differentiation to Th17?

Answer 17

IL-6, IL-1beta

Question 18

What cytokines are released by Th17 and what TF controls it?

Answer 18

Secretes IL-17

TF = RORgammaT

Question 19

What type of infections are Th17 cells important for and what immune cells do they activate?

Answer 19

Protect against fungi by neutrophil recruitment and controlling barrier function

Question 20

What is Tfh?

Answer 20

T follicular helper cells express Bcl-6 to influence B cell response through class switching from IgM. Also provides helper phenotypes to B cells.

Question 21

What allows Tfh to migrate into B cell zone?

Answer 21

CXCR5

Question 22

What is the function of Treg?

Answer 22

To regulate immune responses by restricting costimulatory availability of other T cells and secreting regulatory cytokines.

Question 23

What TF is expressed in Treg?

Answer 23

FoxP3

Question 24

What condition occurs if there is a defect in Treg cells?

Answer 24

AI