Immunology 04. T Cell Subsets

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

Answer 8

Question 9

Answer 9

Question 10

Answer 10

Question 11

Answer 11

Question 12

3 signals needed for the clonal expansion of naive T cells?

Answer 12

3 signals needed for the clonal expansion of naive T cells?

1) Specific antigen signal (Antigen-MHC II complex:TCR + CD4)

2) Co-stimulatory signal (B7:CD28)

3) Cytokine signals

Question 13

4 microbicidal properties of macrophages after Th1 cell activation?

Answer 13

4 microbicidal properties of macrophages after Th1 cell activation?

1) ROS and NO
2) Increased lysosomal enzymes
3) Promote inflammation
4) recruit more leukocytes

Question 14

Activated T cells synthesize the T cell growth factor called ?? and its receptor

Answer 14

Activated T cells synthesize the T cell growth factor called ?? and its receptor

Growth factor is called IL-2

**2 types of receptor as seen below **

Note: Naive t cells have moderate affinity receptor

Mature has the high affinity one

Question 15

Can Macrophages and B lymphocytes present antigens?

Answer 15

Can Macrophages and B lymphocytes present antigens?

Yes.

Macrophages: Phagocytose microbes and display antigen to T cell, which activate the macrophage to kill the microbes

B lymphocytes: ingest antigens and display them to helper T cell which are important for antibody production

Question 16

Does activated T cell still need costimulatory molecule?

Answer 16

Does activated T cell still need costimulatory molecule?

Nope only need for MHC to start killing

Question 17

Function of Th17 cells?

Answer 17

Function of Th17 cells?

Inflammation and neutrophil response

Antimicrobial peptides

Increased barrier integrity

For extracellular bacteria and fungi

Question 18

Give an overview of cell-mediated immunity by T cells, from DC presentation to the actions of activated T cells.

Answer 18

Question 19

How does activated T cell know when to leave the lymph node? What are the mechanisms involved?

Answer 19

How does activated T cell know when to leave the lymph node? What are the mechanisms involved?

Downregulation of CCR7 and L-selectin

Question 20

How does CD8+ CTLs kill cells that are infected with viruses?

[…]

Answer 20

How does CD8+ CTLs kill cells that are infected with viruses?

Release granules containing perforin, granzyme B and granulysin into infected cells

or

FasL

Fas is on infected host cells.

Question 21

Importance of T cell receptor CD3 complex?

Answer 21

Importance of T cell receptor CD3 complex?

Able to transduce intracellular signal which the TCR is unable to

Question 22

Microbes sequestered in vesicles of phagocytes are eliminated by […]
Microbes in cytoplasm of infected host cells are eliminated by […]

Answer 22

Microbes sequestered in vesicles of phagocytes are eliminated by Th1 (via macrophages)
Microbes in cytoplasm of infected host cells are eliminated by CD8+ CTLs

Question 23

The 3 effector proteins that trigger apoptosis that are contained in the granules of CD8 cytotoxic T cells (IMPT!!!)

Answer 23

The 3 effector proteins that trigger apoptosis that are contained in the granules of CD8 cytotoxic T cells (IMPT!!!)

Perforin
Granyzme B
Granulysin

Question 24

The initial interaction of T cells with APC is mediated by what kind of cell-adhesion molecule?

Answer 24

The initial interaction of T cells with APC is mediated by what kind of cell-adhesion molecule?
T cell is initially binded to APC through low-affinity LFA-1:ICAM-1 interactions

Initially weak, but conformation changes in LFA-1 (on the t cell) increases affinity and prolong cell-cell contact

Question 25

Under the presence of IL-12 and IFN-y, what do naive CD4 T cells differentiate to?

Answer 25

Under the presence of IL-12 and IFN-y, what do naive CD4 T cells differentiate to? **TH1 cell.** If IL-4, differentiate into TH2 Viruses and some bacterias induce IL-12 from dendritic cell

Question 26

What are some of the molecules that T cells use to initiate their responses to antigen, and what are the functions of these molecules?

Answer 26

What are some of the molecules that T cells use to initiate their responses to antigen, and what are the functions of these molecules? **TCR, CD4/8** (MHCII/I binding), CD28(co-stimulation), **integrin LFA-1** (adhesion, migration)

Question 27

What are the events that happen after T cell activation?

Answer 27

What are the events that happen after T cell activation? **TCR Signaling** **Clonal expansion** Differentiation and development of **Memory T cell**

Question 28

What are the events that lead to T cell activation? 3 events

Answer 28

What are the events that lead to T cell activation? 3 events **Recognition** of MHC peptide **Adhesion** **Costimulation**

Question 29

What are the important receptors in T-cell trafficking?

Answer 29

What are the important receptors in T-cell trafficking? 1) **S1P**: T-cell trafficking OUT of lymph nodes 2) **CCR7**: Expressed in naive T cells, trafficking INTO secondary lymphoid organs (Recognises **CCL19/21** of secondary lymphoid organ) 3)** L-selectin**: Expressed in naive T cells, trafficking INTO secondary lymphoid organs "S1P gtfo, CCR7 L-selectin welcome home"

Question 30

What are the two types of memory T cells? Where do they go?

Answer 30

What are the two types of memory T cells? Where do they go? **Central memory T cells**: remain in the lymphoid tissues **Effect memory T cells**: possess effector phenotype and reisde in peripheral tissues

Question 31

What do viruses and bacteria induce dendritic cells to secrete in terms of Cytokines?

Answer 31

What do viruses and bacteria induce dendritic cells to secrete in terms of Cytokines? Dendritic cells: **IL-12, **then IL-12 can activate NK cells to produce **IFN-y ** IL-12 + IFN-y = Naive CD4 T cells differentiate into TH1 cells

Question 32

What does TH1 cell and TH2 cell produce? and what are the effects?

Answer 32

What does TH1 cell and TH2 cell produce? and what are the effects? TH1: ***IFN-y (gamma***) TH2: ***TGF-B*** (transforming growth factor beta) and ***IL-10 , IL-4*** Inhibit each other lol

Question 33

What happens to T cells with specific signal but without a costimulatory signal?

Answer 33

What happens to T cells with specific signal but without a costimulatory signal? **Anergy (T cell inactivation)**

Question 34

What influences the functional differentiation of CD4+ T cells?

Answer 34

What influences the functional differentiation of CD4+ T cells? **Cytokines**!

Question 35

What is costimulation? What is the physiological significance of costimulation? Waht are some of the ligand-receptor pairs invovled in costimulation?

Answer 35

What is costimulation? What is the physiological significance of costimulation? Waht are some of the ligand-receptor pairs invovled in costimulation? **second signal** independant of specific antigen signalling. **B7:CD28**

Question 36

What is the most potent APC for activating naive t cell?

Answer 36

What is the most potent APC for activating naive t cell? **Dendritic Cell**

Question 37

What is the principal growth factor for t cells? Why do antigen specific t cells expand more than other bystander t cells on exposure to an antigen?

Answer 37

What is the principal growth factor for t cells? Why do antigen specific t cells expand more than other bystander t cells on exposure to an antigen? IL2!! Activated T cells upregulates expression of **BOTH IL2 and IL2 receptors**, hence increased clonal expansion compared to bystanders Bystanders dont upregulate expression of IL2 receptors spontaneously, so they cant respond to the ocean of IL2 around them anyways.

Question 38

What is the principle co-stimulatory molecule expressed on APC? And what do they bind to?

Answer 38

What is the principle co-stimulatory molecule expressed on APC? And what do they bind to? B7 molecules on APC. Binds to T cell protein **CD28** "B7:CD28"

Question 39

What kind of pathogens induce the secretion of **IL-4?** What do naive CD4 T cells differentiate into under this influence?

Answer 39

What kind of pathogens induce the secretion of IL-4? What do naive CD4 T cells differentiate into under this influence? Worms and other pathogens (usually not virus and bacteria). The t cells differentiate into TH2 cells