Test 4: T cell effector functions

Question 1

What do T cells interact with in order to leave the lymph nodes and enter circulation?

Answer 1

High Endothelial Venules (HEVs)

Question 2

What 4 things are required for proliferation and differentiation of CD4 cells?

Answer 2

• antigen recognition from dendritic cell via class II MHC
• B7-1/2 with CD28 on T cell
• CD40 with CD40L on T cell
• autocrine/paracrine function of IL-2

Question 3

What plays an essential role in activating CD8 cells?

Answer 3

Dendritic cells

Question 4

What other cell could help with differentiation into CTLs?

Answer 4

CD4+ helper cells

Question 5

What is the immunological synapse?

Answer 5

The site of contact between T cells and APCs to where T cell proteins are mobilized

Question 6

What T cell molecules move to the immunological synapse?

Answer 6

TCR, CD3 and zeta chains, CD4/8 co-receptors, etc

Question 7

What causes differentiation of TH1 CD4 cells?

Answer 7

IL-12 from the APC and IFN-gamma from NK cells (inflammatory cytokines); CD40 engagement

Question 8

What is the effect of IFN-gamma released from a TH1 cell on a macrophage (or other APC)?

Answer 8

• kills intracellular parasite that has been ingested by macrophage via more ROS and increased expression of MHC and costimulators (B7)
• also releases inflammatory response to kill surrounding cells (TNF, IL-1, chemokines, IL-12)

Question 9

What is the effect of IFN-gamma released from a TH1 cell on a B cell?

Answer 9

-causes IgG production to stimulate opsonization and complement cascade

Question 10

What is secreted in order to activate/enhance neutrophil microbial killing?

Answer 10

Leukotoxin and Tumor Necrosis Factor (LT and TNF)

Question 11

As opposed to TH1 cells, TH2 cells differentiate in the absence of what?

Answer 11

inflammatory cytokines and IFN-gamma

Question 12

What is the principal function of TH2 cells?

Answer 12

promote IgE and eosinophil/mast cell-mediated reactions

Question 13

What do eosinophils/mast cells protect against?

Answer 13

Helminthic infections (intestinal worms)

Question 14

What does the release of IL-4 from TH2 cells cause?

Answer 14

Isotype switching of antibodies to IgE

Question 15

What does IL-5 do when released from TH2 cells?

Answer 15

attracts and activates eosinophils so that it will engage the worm

Question 16

What is the alternate function of IL-4 and IL-13?

Answer 16

Alternate macrophage activation for wound repair, tissue fibrosis, and suppression of inflammation

Question 17

What is the best sign of CTL differentiation?

Answer 17

membrane-bound cytoplasmic granules containing perforin (like MAC complex) and granzymes (induces apoptosis via caspase activation)

Question 18

Where are perforin and granzymes produced?

Answer 18

De novo in response to a stimulated CD8 cell

Question 19

Why do CTLs secrete IFN-gamma, lymphotoxin and TNF?

Answer 19

activate macrophages and induce inflammation

Question 20

What other method induces apoptosis of a cell from CTLs?

Answer 20

Fas interaction on the CTL

Question 21

What are expressed on endothelial cells at site of infection to bind T cells?

Answer 21

Adhesion molecules in post capillary venules

Question 22

What happens to the T cell if it doesn’t recognize any antigens?

Answer 22

Returns to circulation

Question 23

What else can a CD4 cell differentiate in to besides TH1 and TH2?

Answer 23

CD17

Question 24

When does CD17 differentiation happen?

Answer 24

in response to EXTRACELLULAR bacteria/fungi

Question 25

What is released from CD17 cells?

Answer 25

inflammatory response (IL-6) and IL-17 to  attract and activate PMNs
-effect is enhanced by antibody production (humoral response)