Cell Mediated Immunity

Question 1

Describe an immature dendritic cell

Answer 1

Main function is to CAPTURE antigen; high levels of receptors, low levels of MHC and co-stimulatory molecules.

Question 2

Describe a mature dendritic cell.

Answer 2

Main function is to PRESENT antigen; Opposite receptor and molecule expression than immature dendritic cell.

Question 3

What does a newly activated T cell secrete?

Answer 3

IL-2 and express high affinity IL-2 receptor. The low affinity receptor is expressed on naive T cells.

Question 4

Describe the composition of the Low affinity receptor.

Answer 4

Dimer of beta and gamma chain

Question 5

Describe the composition of the high affinity receptor.

Answer 5

Trimer of beta, gamma and alpha chain; Always expressed on regulatory T cells.

Question 6

What are the fates of cells in clonal expansion?

Answer 6

They will either become effector cells or memory cells.

Question 7

What is the role of chemokines and chemokine receptors?

Answer 7

Changes in chemokine receptors and adhesion molecules allow newly activated T cells to exit lymph nodes or spleen, enter the blood circulation and move to the site of inflammation.

Question 8

How does a dendritic cell control T cell differentiation?

Answer 8

The immunological synapse between a professional APC and Th0 cell. The cytokines released determine the type of T cell.

Question 9

What determines which cytokines are produced by a dendritic cell or other APC while interacting with a Th0?

Answer 9

1. Host genetics
2. Type of infection
3. Type of TLR engaged on the APC

Question 10

Understand the type of signal chart and picture

Answer 10

Pg 76

Question 11

Which cytokine makes a Th0 differentiate into a Th1 cell?

Answer 11

IL-12; Happens during an intracellular infection. IL-18 promotes a Th1 response by amplifying the effects of IL-12. Both IL-12 and 18 help activate NK cells.

Question 12

Which cytokine makes a Th0 differentiate into a Th2 cell?

Answer 12

IL-4; Happens during an extracellular infection. Mast cells and basophils make IL-4.

Question 13

Which cytokine makes a Th0 differentiate into a Th17 cell?

Answer 13

IL-23; TGF-B and IL-6 in their differentiation. Response to extracellular bacteria and fungi. Made by dendritic cells and macrophages.

Question 14

Which cytokine makes a Th0 differentiate into a Treg?

Answer 14

IL-10/TGF-F; Must be in the absence of IL-6.

Question 15

Which cytokine does Th1 cells secrete?

Answer 15

They secrete IFN-y and IL-2 which stimulates clonal expansion.

Question 16

What are the effects of IFN-y secretion?

Answer 16

1. Activates macrophages
2. Upregulates MHC 1 and 2 on APCs and endothelium.
3. Inhibits development of Th2 and Th17.
4. Activates isotype switching in B cells to make IgG

Question 17

Describe the positive feedback cycle between macrophages and Th1 cells.

Answer 17

IFN-y activated macrophages make IL-12, which promotes Th1 cell development. Th1 cells then secrete IFN-y; Delay type hypersensitivity.

Question 18

What does Th2 cells secrete?

Answer 18

IL-4, 21,5,6,10 and 13.

Question 19

What does IL-4 do?

Answer 19

1. Induce Th0 into Th2
2. Suppresses inflammatory function of macrophages
3. In conjunction with with IL-21,5 and 6, it promotes proliferation of B cells and isotype switching to IgG and IgM
4. In conjunction with IL-13 it promotes isotype switching to IgE and wound healing by alternative macrophages.

Question 20

What does IL-13 do?

Answer 20

Stimulates mast cell proliferation

Question 21

What does IL-10 do?

Answer 21

Surpresses Th1 response.

Question 22

Which cells make IL-17?

Answer 22

Th17 cells;

1. Stimulates changes in vessels that increase chemotaxis of neutrophils, especially in skin and mucosa.
2. Defense against extracellular bacteria and parasites.
3. Inhibited by Th1 or Th2 response

Question 23

Know chart on pg 84

Answer 23

see coursepack

Question 24

How do CD8s stop an intracellular pathogen?

Answer 24

Does not require co-stimulation through CD28/B7 interaction; Induces apoptosis.

1. Cytotoxic granules containing perforin and granzymes.
2. Fas ligand on CD8 binds to Fas receptor on target cell.
3. CD8s secrete IFN-y which activates macrophages to phagocytose infected cells.

Question 25

What are the two mechanisms of controlling T cell responses?

Answer 25

1. Lack of stimulatory signals
2. Inhibitory receptors
3. Death receptors