Lecture 15 - Antigen-Presenting Cells II

Question 1

Prototypical mediators of DC activation and maturation

Answer 1

TLRs

Question 2

Do activated DCs move actively or passively to lymph nodes?

Answer 2

Actively

Question 3

DCs in the epithelium of the skin

Answer 3

Langerhans cells

Question 4

How do Langerhans cells sit in the skin?

Answer 4

Intimately associated with keratinocytes, to keep skin integrity (associate with E-cadherin).

Question 5

How do activated Langerhans cells reach lymph nodes?

Answer 5

Express CCR7

CCR7 detects chemokines CCL19, CCL21.

Question 6

Which part of lymph nodes do activated DCs move to?

Answer 6

Paracortex

Question 7

How do naive T cells enter lymph nodes?

Answer 7

Via blood, through the walls of high endothelial venules

Question 8

How do DCs enter lymph nodes?

Answer 8

Via lymphatics

Question 9

Where are tumour antigens presented?

Answer 9

MHCI

Question 10

NFkB dimer stimulated by TLR binding

Answer 10

p50, p65

Question 11

How do DCs detect intracellular bacteria?

Answer 11

Inflammosomes

Question 12

How do DCs detect facultative intracellular bacteria?

Answer 12

Surface via TLR5

Endosome via TLR3, TLR11

Question 13

How do DCs detect viruses?

Answer 13

Extracellular or engulfed - TLR3, TLR9 in phagosome

Intracellular - Inflammasome, MDA5, RIG1

Question 14

Basic overview of DCs
1)
2)
3)

Answer 14

1) Mostly exist in immature state of high phagocytic activity, low presentation
2) Possess a wide array of PRRs to integrate environmental cues
3) Stimulation initiates maturation, lowers phagocytosis, increases presentation, migration to lymph node

Question 15

Surface chemokine receptor expressed by mature DCs

Answer 15

CCR7

Question 16

How is MHCI/peptide complex transported to cell surface?

Answer 16

Via Golgi

Question 17

What is DC cross-presentation?

Answer 17

Extracellular, phagocytosed antigens being presented on MHCI, to stimulate CD8+ T cells

Question 18

Why is cross-presentation used?
1)
2)

Answer 18

1) If a virus kills DCs, so DCs need to present to CD8+ T cells without being infected (need infection to present on class I by direct pathway)
2) If a virus is present in the periphery where there are no naive CD8+ T cells (EG: herpes simplex). DCs can take up antigen, present on MHCI and travel to lymph nodes.

Question 19

DC surface proteins expressed upon activation for T cell activation

Answer 19

CD80, CD86

Question 20

How are DCs stopped from eliciting a T cell response against self antigens?
1)
2)

Answer 20

1) CD80 and CD86 are only upregulated if a foreign antigen stimulates PRRs.
2) CD80, CD86 needed to stimulate a T cell. Even if a T cell is cognate with DC presenting a self antigen, without CD80/CD86, nothing will happen

Question 21

Types of antigens presented through cross-presentaiton

Answer 21

Viral antigens

Question 22

Pathogen presented from receptor-mediated endocytosis

Answer 22

Extracellular bacteria

Question 23

Pathogen presented from macro-pinocytosis

Answer 23

Extracellular bacteria, soluble antigen, viral antigen

Question 24

Signal 1, 2 and 3

Answer 24

1) TCR - MHC interaction
2) CD80/CD86 - CD28 interaction
3) Cytokines to bias T cell type

Question 25

Signal 1 role

Answer 25

Activation of T cell

Question 26

Signal 2 role

Answer 26

Survival of T cell

Question 27

Signal 3 role

Answer 27

T cell differentiation

Question 28

Do activated CD8+ T cells need a signal 2?

Answer 28

No.

They will be in the periphery, killing non-professional APCs, which can’t costimulate

Question 29

Type of T cell that doesn’t require signal 2

Answer 29

Activated CD8+ T cell