T Cell Mediated Immunity

Question 1

What is the only cell that can activate naive T cells?

Answer 1

Dendritic cells

Question 2

What kind of T cells activate B cells and macrophages?

Answer 2

CD4+ T cells

Question 3

What is the purpose of CCR7 in DCs?

Answer 3

It helps localize the activated DC to lymphatic endothelium.

Question 4

Where do naive T cells enter the lymph nodes from?

Answer 4

High endothelium venules

Question 5

What two T cell transmembrane proteins are found on both helper and cytotoxic T cells that play a key role in signal transduction?

Answer 5

CD3 and ζ chain

Question 6

What is the ligand for the T cell surface molecule, CD28?

Answer 6

CD80 (B7), found on APCs

Question 7

What are the inhibitory molecules found on the surface of T cells?

Answer 7

CTLA-4 and PD-1

Question 8

What does CTLA-4 inhibit?

Answer 8

CD80 (B7), which is normally activated by CD28

Question 9

What molecules are upregulated as a result of T cells and APCs binding their the MHC/TCR complexes?

Answer 9

CD40L expression is upregulated in T cells; CD40 is constitutively expressed on APCs. CD80 (B7) expression is upregulated on APCs; CD28 is constitutively expressed on T cells.

Question 10

Describe the initiation of the intracellular signaling cascade in T cells following the formation of the immunologic synapse.

Answer 10

Immunoreceptor tyrosine-based activation motifs (ITAMs) are activated. Lck phosphorylates and activates ZAP-70 on ζ chain.

Question 11

What membrane proteins are upregulated as a result of T cell activation?

Answer 11

CD40L and CD25 (IL-2R α chain)

Question 12

What is the purpose of IL-2 in T cells?

Answer 12

It is an autocrine signal that triggers proliferation and differentiation.

Question 13

The expression of what molecule prevents activated T cells from migrating out of the lymph node? What does it bind to?

Answer 13

CD69 binds to S1PR

Question 14

What are the main targets for Th1 cells?

Answer 14

Macrophages and B cell class switching to IgG. Also CD8+ cloning and activation.

Question 15

What are the main targets for Th2 cells?

Answer 15

Eosinophils/Mast cells in response to allergens and helminths, and B cell class switching to IgE. Also supports alternative macrophage development.

Question 16

What are the main targets for Th17 cells?

Answer 16

Neutrophils and barrier function in tissue cells

Question 17

What is the main target for Tfh cells?

Answer 17

B cells for antibody production

Question 18

Describe T regulatory cells (Tregs). What do they express and secrete?

Answer 18

A type of CD4+ cells that constitutively express CTLA-4 and CD25. They secrete IL-10 and TGF-β. Uses novel transcription factor FOXp3.

Question 19

Describe gamma delta T cells.

Answer 19

Found in high numbers in gut mucosa. Limited diversity of peptides recognized, but can recognize non-protein Ag and it does not require MHC presentation.

Question 20

What do Th1 cells proliferate in response to? What do they secrete?

Answer 20

Responds to IL-12 and IFN-γ. Secretes IL-2 and IFN-γ.

Question 21

What is the novel transcription factor for Th1 cells?

Answer 21

T-bet

Question 22

How do Th1 cells affect APCs once activated?

Answer 22

They stimulate HLA II and B7 (CD80) expression

Question 23

What do Th2 cells proliferate in response to? What do they secrete?

Answer 23

Responds to IL-4. Secretes IL-4, IL-5, IL-13.

Question 24

What is the novel transcription factor for Th2 cells?

Answer 24

GATA-3

Question 25

What is the difference between classically activated and alternatively activated macrophages?

Answer 25

Classic: activated by Th1, leads to phagocytosis and killing of many bacteria and fungi. Alternative: activated by Th2, leads to anti-inflammatory effects, wound repair, and fibrosis.

Question 26

What do Th17 cells proliferate in response to? What do they secrete?

Answer 26

Responds to IL-1 and IL-6. Secretes IL-17 and IL-22.

Question 27

What is the novel transcription factor for Th17 cells?

Answer 27

RORγt

Question 28

What is the purpose of CD44 in T helper cells?

Answer 28

It helps with cell adhesion and migration into peripheral tissues.

Question 29

What are the two main killing mechanisms for cytotoxic T cells?

Answer 29

1. Cytotoxins: granzymes and perforin | 2. FasL and Fas (CD95) induction of apoptotic pathways

Question 30

What are NK cells enhanced and inhibited by?

Answer 30

Enhanced by IFN-α, IFN-β, and IL-2. Inhibited by HLA I.

Question 31

What are the surface markers for NK cells?

Answer 31

CD16 and CD56

Question 32

What do memory T cells increase the expression of in order to prevent apoptosis?

Answer 32

Bcl-2

Question 33

What is the role of the PD-1 receptor?

Answer 33

Expressed on T cells, B cells, and myeloid cells. Leads to negative regulation of T cells.

Question 34

Which interleukins are required for the survival of memory T cells?

Answer 34

IL-7 and IL-15

Question 35

What happens to CD4+ and CD8+ cells during chronic viral infections?

Answer 35

They become exhausted and are unable to respond to the virus.

Question 36

What is toxic shock syndrome’s (TSS) affect on the immune system?

Answer 36

The toxin released acts as a superantigen and leads to nonspecific T cell activation. Binds to β chain of TCR.