T-Cell Activation and Effector Mechanisms

Question 1

What are the two types of TCRs? Which is most common (95% of T cells have it)

Answer 1

• Alpha-beta - most common

- Gamma-delta

Question 2

Do alpha-beta TCRs recognize the peptide, the MHC molecule, both, or neither?

Answer 2

Both

Question 3

What four proteins make up the CD3 complex?

Answer 3

Gamma, delta, epsilon, zeta

Question 4

What co-receptor do CTLs express?

Answer 4

CD8

Question 5

What co-receptor do Th cells express?

Answer 5

CD4

Question 6

What proteins are used as costimulation to activate naive T cells? What do they bind to?

Answer 6

B7 proteins on activated dendritic cells

Bind to CD28 TCRs on cell surface

Question 7

What growth factor/cytokine can helper T cells supply killer T cells, allowing the CTLs to proliferate?

Answer 7

IL-2

Question 8

What provides co-stimulation for B cell activation?

Answer 8

A helper T cell through CD40L

Question 9

What pattern recognition receptor on dendritic cells sense LPS?

Answer 9

TLR 4

Question 10

What cytokine do dendritic cells produce in lymph nodes when they have been activated by macrophages and other cells? What cell does this cytokine help activate?

Answer 10

IL-12 - this helps activate virgin Th cells (Th1)

Question 11

What cytokines do Th1 cells produce? What do they do?

Answer 11

• TNF: activates macrophages and NKCs
• IFN-γ: influences class switching in B cells
• IL-2: recharges NKCs and stimulates growth of CTL’s and Th1 cells as well

Question 12

What cytokines do Th2 cells produce? What do they do?

Answer 12

• IL-4: stimulates proliferation of Th cells, B cell growth, production of IgE Abs
• IL-5: stimulates B cell production of IgA
• IL-3: stimulates production of mucus in GI system

Question 13

What type of infection are Th17 helper cells useful in?

Answer 13

Fungal infections

Question 14

What are Th0 helper cells?

Answer 14

“Unbiased” cells - dendritic cells tell them where to go, but not how to differentiate - they do so based on the cytokine environment they travel to

Question 15

What cytokine do Th1 and Th2 cells produce to provide negative feedback on each other?

Answer 15

Th1 cells make IFN-γ to decrease Th2 cell production

Th2 cells produce IL-10 to reduce Th1 cell production

Question 16

What type of Th and B cells do Peyer’s patches produce?

Answer 16

Th2 helper cells

B cells that secrete IgA Abs

Question 17

Explain how the tuberculin (PPD) test works.

Answer 17

If you’ve been infected with Tb or have it, memory Th1 cells recognize tuberculin fragments presented by DC’s under the skin. These Th1 cells secrete IFN-γ and TNF which activate tissue macrophages, recruit neutrophils, cause redness and swelling - positive TB test. You have to wait a few days so memory Th cells can be reactivated.

Question 18

What are the two ways CTLs kill cells?

Answer 18

1. Perforin - binds to membranes, drills holes and Granzyme B - triggers apoptosis cascade
2. Surface protein - FasL - binds to Fas on target’s surface –> apoptosis

Question 19

What type of Th and B cells will lymph nodes produce after a skin puncture?

Answer 19

Th1 cells

B cells secreting IgG Abs