T cell effectors

Question 1

What cytokines are needed for a naive CD4+ T cell to develop into a Th1 cell?

Answer 1

**IFNγ **(produced by NK cells)

IL-12 (produced and secreted by DCs or MØs)

Question 2

What transcription factors are needed for a naive CD4+ T cell to develop into a Th1 cell?

Answer 2

T-bet

Question 3

What cytokines to Th1 cells produce?

Answer 3

IFN-γ

TNF

Question 4

What kind of pathogens do Th1 cells target?

Answer 4

Intracellular pathogens b/c Th1 cells are engaged in host defense

Question 5

What pathogenic process are Th1 cells involved in?

Answer 5

Autoimmunity

Question 6

What activities are Th1 cells engaged in?

Answer 6

• Activate macrophages via CD40-CD40L interaction and IFN-gamma (Help phagocytosis)
• Stimulate B cell class-switch to IgG3 (great opsonizer), while suppressing IgG4 (Help opsonization)

Question 7

What does IFN-gamma do?

Answer 7

IFN-gamma triggers the JAK-STAT pathway to:

Activate MØs → enhanced killing of phagocytosed bacteria & secretion of inflammatory cytokines

Upregulate MHC class I and II expression by APCs

Upregulate expression of costimulatory molecules (e.g., CD40, B7 on APCs)

Promote CD4+ differentiation into Th1 cells and inhibit differentiation into Th2 cells

Question 8

What cytokines are needed for a naive CD4+ T cell to develop into a Th2 cell?

Answer 8

**IL-4 **(produced and secreted by DCs and mast cells)

Question 9

What transcription factors are needed for a naive CD4+ T cell to develop into a Th2 cell?

Answer 9

GATA3

Question 10

What cytokines do Th2 cells produce?

Answer 10

IL-4

IL-5

IL-13

Question 11

What kind of pathogens do Th2 cells target?

What else are they responsible for?

Answer 11

Parasites (e.g., helminths) b/c they are also involved in host defense

They are also responsible for allergy and asthma

• Th2 cells cause:
  
  • mast cell proliferation
  • B cell isotype switching to IgE
  • Proliferation of B cells

Question 12

What pathogenic process are Th2 cells involved in?

Answer 12

Tumor growth (cancer)

Question 13

What does IL-4 do?

Answer 13

• Stimulates development of Th2 cells
• Stimulates B cell isotype switching to IgG4 (inhibit IgG3)
• With IL-13:
  
  • Stimulates leukocyte recruitment

Question 14

What does IL-5 do?

Answer 14

Activates eosinophils

Question 15

What cytokines are needed for a naive CD4+ T cell to develop into a Th17 cell?

Answer 15

TGF-β

IL-6 (produced and secreted by DCs)

Question 16

What transcription factors are needed for a naive CD4+ T cell to develop into a Th17 cell?

Answer 16

RORγT

Question 17

What cytokines do Th17 cells produce?

Answer 17

IL-17

IL-21

Question 18

What kind of pathogens do Th17 cells target?

Answer 18

Extracellular pathogens (e.g., bacteria, fungi) b/c they also engage in host defense

Question 19

What effect do Th17 cells have on certain innate immune system cells?

Answer 19

They ⇡chemokine & cytokine production in MØs, neutrophils, and endothelial cells.

Question 20

What pathogenic processes are Th17 cells involved in?

Answer 20

**Inflammation **

Autoimmunity (heavily)

Question 21

What cytokines are needed for a naive CD4+ T cell to develop into a T_reg cell?

Answer 21

TGF-β

Question 22

What transcription factors are needed for a naive CD4+ T cell to develop into a T_reg cell?

Answer 22

FOXP3

Question 23

What cytokines do T_reg cells produce?

Answer 23

TGF-β

IL-10

Question 24

What is the function of T_reg cells?

Answer 24

Immunosuppression

Question 25

What cytokines and cytotoxins do CD8+ T cells secrete?

Answer 25

• Cytokines:
  
  • IFN-γ
  • LT
• Cytotoxins:
  
  • Perforin
  • Granzyme

Question 26

NK Cells

Answer 26

= Lymphocytes (comprise 8-10% of peripheral blood lymphocytes)

• Release perforin and granzyme
• Do not require CD4+ T cell help
• See less MHC Class I
• Mainly attacks sick cells

CD56

Question 27

CTLs

Answer 27

= CD8+ T cells

• Release perforin and granzyme
• **Require **CD4+ T cell help
• Require MHC Class I and only works if cells have antigen on cell surface/MHCI pocket
• Mainly involved in graft rejection

Question 28

What does LFA-1 do?

Answer 28

• LFA-1 is an adhesion molecule on CD8+ T cells that binds to ICAM-1 on target cells
• LFA-1 & ICAM-1 interaction:
  
  • maintains close apposition b/w CTL and target cell
  • helps prevent collateral damage to other host cells and the CTL itself by triggering cytoskeletal rearrangement in the CTL that leads to granule accumulation mostly at the site of contact b/w the CTL and target cell → target cell death (w/o death of other host cells)

Question 29

What does FasL do?

Answer 29

• FasL on CTLs interacts with Fas on target cells → apoptosis of target cells
• Immune-priviledged sites have Fas