Lec 45: Adaptive Immunity II (NSD)

Question 1

What are the two subsets of helper T cells?

Answer 1

Th1 and Th2

Question 2

What type of cells to Th1 cells attach to?

Answer 2

Dendritic cells and Macrophages

Question 3

What receptors do Th1 cells directly bind to?

Answer 3

MHC II-antigen complexes; CD40

Question 4

What are the primary cytokines secreted by TH1 cells?

Answer 4

Interferon-gamma (IFN-gamma); Interleukin-2 (IL-2)

Question 5

What does interferon gamma do?

Answer 5

1. Activates “resting” macrophages

2. Inhibits Th2 activity

Question 6

What major cytokine is produced by APCs when they come in contact with intracellular pathogens?

Answer 6

Interleukin-12 (IL-12)

Question 7

What effect does IL-12 have on T cells and natural killer (NK) cells?

Answer 7

1. CD8+ and NK cells: More IFN-gamma secretion and increased cytolytic activity
2. Naive CD4 cells –> Th1 cells –> increased IFN-gamma secretion

Question 8

What type of cells to Th2 cells attach to?

Answer 8

B cell presenting specific antigen

Question 9

What receptors do Th2 cells directly bind to?

Answer 9

MHC II-antigen complexes; CD40

Question 10

What are the primary cytokines secreted by TH2 cells?

Answer 10

IL-4; IL-5

Question 11

What effect do IL-4 and IL-5 have on their target cells and on Th1 cells?

Answer 11

1. B-cell differentiation and antibody production

2. Inhibition of Th1 cells

Question 12

What is the primary function of CD8 cells?

Answer 12

Induce apoptosis in cells infected with viruses/intracellular pathogens

Question 13

What happens to a virus once inside a dendritic cell?

Answer 13

1. Viral proteins are produced in the cytosol on the cell
2. Viral proteins are degraded
3. Degraded proteins are transported from cytosol to ER
4. Peptide-MHC class 1 complexes formed in ER
5. Complexes move to cell surface
6. Complexes are recognized by CD8 cytolytic lymphocytes

Question 14

What are the differences in the 3 major pathways for activation in naive CD8 (CTL) cells?

Answer 14

1. Without help from CD4 cells
   1a. CTL binds to MHC I-antigen complex and B7 on virus-infected cell
   1b. IL-2 is produced by CTL and drives its own proliferation and differentiation

2+3 With help from CD4 cells

2. Nearby CD4 T cell helps CTL binding by inducing B7 expression on surface of APC
3. Nearby CD4 T cell helps CTL binding by releasing IL-2

Question 15

What types of cells can naive CD8 cells differentiate into?

Answer 15

Effector T cells or memory T cells

Question 16

How do naive T cells differentiate and reach infected sites?

Answer 16

1. Naive T cells meet dendritic APCs n the lymph node
2. Naive T cells develop into effector cells in the lymph node
3. Effector T cells exit into efferent lymph and travel to infected cells

Question 17

How do CD8+ cells (CTLs) kill the cells they target?

Answer 17

1. Recognize MHC I complex on infected cells
2. CTL releases cytolytic granules on surface of the infected cell
3. Infected cell begins to lyse; apoptosis occurs
4. Recognize MHC 1 complex and Fas on neighboring infected cell and process repeats (if applicable)