Theme 7: CD4 Subsets

Question 1

What induces T cell differentiation?

Answer 1

Cytokines

Question 2

What are the main functions of CD4+ T helper cells?

Answer 2

1) Viral clearance
2) Worm expulsion
3) Intracellular/extracellular pathogens
4) Tumor defense/progression

Question 3

What are some examples of cytokine sources?

Answer 3

DCs (most potent), macrophages, tissue cells, eosinophils/basophils, other T cells

Question 4

Describe the characteristics of Tregs

Answer 4

1) Induced by IL-2 and TGF-β
2) Master regulator = FoxP3
3) Releases IL-10 and TGF-β
4) Suppresses immune responses
5) May be involved in inhibiting antitumor response

Question 5

Describe the characteristics of Tfh

Answer 5

1) Induced by IL-6 and IL-21
2) Master regulator = Bcl-6
3) Releases IL-4 and IL-21
4) Affinity maturation, antibody production

Question 6

Describe the characteristics of TH1

Answer 6

1) Induced by IL-12, IFN-y, IL-18
2) Master regulator = T-Bet
3) Releases IFN-y and TNF
4) Targets macrophages, neutrophils, and epithelia
5) Combats intracellular pathogens, activates macrophages, induces lysis, antimicrobial production
6) May be involved in tissue inflammation (autoimmunity)

Question 7

Describe the characteristics of TH2

Answer 7

1) Induced by IL-4
2) Master regulator = GATA3
3) Releases IL-4, IL-5, and IL-13
4) Targets eosinophils, basophils, mast cells, and epithelia
5) Combats extracellular pathogens (worms like helminths), histamine release, mucus production
6) May be involved in allergy

Question 8

Describe the characteristics of TH17

Answer 8

1) Induced by IL-6, IL-23, TGF-β
2) Master regulator = RORyt
3) Releases IL-17A, IL-17F, IL-22
4) Combats extracellular pathogens at barrier sites
5) May be involved in autoimmunity and tissue inflammation

Question 9

Describe the characteristics of TH9

Answer 9

1) Induced by IL-4 and TGF-β
2) Master regulator = PU.1
3) Releases IL-9
4) Combats extracellular pathogens

Question 10

Describe the characteristics of TH22

Answer 10

1) Induced by IL-6 and TNFα
2) Master regulator = AHR
3) Releases IL-22
4) Combats extracellular pathogens in skin

Question 11

Describe the process of TH1 induction and responses

Answer 11

1) IL-12 (IFN-y and IL-18) is released by DCs and induces T-bet
2) Interaction of TH1 with DCs induces licensing
3) Release of IFN-y, TNF
4) Increased phagocytosis, increased ROS, increased killing of intracellular pathogens by macrophages
5) Antiviral response in epithelial cells and apoptosis

Question 12

Describe the process of DC licensing by CD4+ Th1

Answer 12

1) Involves TCR interactions with MHC-antigen
2) Involves CD28:B7 and CD40L:CD40 (cross presentation)
3) Involves CD27:CD70 interactions (survival, T-bet and NFkB activation)

Question 13

Describe the process of TH2 induction and responses

Answer 13

1) IL-4 is released by basophils and induces GATA3
2) Releases IL-4,5,13
3) Histamine release in mast cells, eosinophils, basophils
4) B cell IgE production
5) Macrophage cytokine production to promote TH2 environment
6) Epithelia mucus secretion and peristalsis

Question 14

What is the pattern observed regarding TH1 and TH2 responses and leishmania infection?

Answer 14

1) Type I response allows for expulsion of infection
2) Type II response prevents phagocytes from being able to kill the pathogen
3) Individuals with responses skewed in favour of type II are susceptible to leishmania

Question 15

What is the pattern observed between autoimmunity and helminth infection?

Answer 15

1) Countries with pervasive helminths (worms) infection have higher TH2 responses and less incidence of autoimmunity
2) Countries with higher rates of autoimmune disease do not have helminths and are more skewed towards TH1 response

Question 16

Describe the process of TH17 induction and responses

Answer 16

1) Comes from the lymph node in response to IL-6 and TGF-β, induces RORγt
2) Releases IL-17 and IL-22
3) IL-22 promotes barrier function and induces antimicrobial production
4) IL-17 acts on epithelial cells and other cells to induce CXCL8 and G-CSF production (neutrophil recruitment and granulopoiesis)

Question 17

Which antibody isotype does a TH1 environment induce?

Answer 17

IgG

Question 18

Which antibody isotype does a TH2 environment induce?

Answer 18

IgE

Question 19

Which antibody isotype does a TH17 environment induce?

Answer 19

IgA

Question 20

What type of response is best for fighting tumors?

Answer 20

TH1 > TH2, because TH1 induces proinflammatory status of macrophages