Lecture 9

Question 1

Which branch of the adaptive immune system combats infection with intracellular pathogens?

Answer 1

Cell mediated immunity (CMI):

-CD4+ Th1 cells and CD8+ cytotoxic T lymphocytes

Question 2

What role do CD4+ Th1, Th2, and Th17 play?

Answer 2

• Th1 and Th2 interact with B cells to promote expression of high affinity antibodies against extracellular bacteria and helminths
• Th17-combat infection with extracellular bacteria and fungi through stimulation of defensin production by EFC and recruitment of neutrophils

Question 3

Where does differentiation of naive CD4+ Th cells into effector subsets occur?

Answer 3

peripheral lymphoid organs and directed by cytokines

Question 4

Which cytokines drive differentiation of CD4 T cells into Th1 effector cells?

Answer 4

-cytokines IL-12 and IFN-gamma

Question 5

Which cells produce IL-12 and IFN-gamma?

Answer 5

• IL-12 by macrophages

- IFN-gamma- by NK

Question 6

Which cytokine drives differentiation of CD4 T cells into Th2 effector cells?

Answer 6

• IL-4 produced by mast cells, tissue cells, and T cells

- activates transcription factors that promote differentiation into Th2 subset

Question 7

Which cytokines drive differentiation of CD4 T cells into Th17 effector cells?

Answer 7

-cytokines IL-1, IL-6, and IL-23 and are secreted by DCs in response to PAMPS expressed by fungi and extracellular bacteria

Question 8

What is the primary role of Th1 cells?

Answer 8

• activate macrophages for enhanced destruction of ingested microbes
• promotes classical pathway of macrophage activation by secretion of IFN-gamma and expression of CD40L
• macrophages upregulate enzymes that stimulate ROS and NO that kill microbes
• increase cytokines such as TNF for promoting leukocyte recruitment
• increase MHC molecules that increase presentation of antigens to T cells at infection site
• increase IL-12 to reinforce Th1 differentiation

Question 9

Which enzymes do CTLs contain?

Answer 9

• perforin-create pores in target cell membrane allowing granzymes to enter
• granzymes-induce cell to undergo apoptosis

Question 10

What is the primary roles of Th2 cells?

Answer 10

• eosinophil recruitment through IL-5
• stimulation of IgE expression by B cells through IL-4
• stimulation of alternative pathway of macrophage activation through IL-4 and IL-13

Question 11

How does the degree of Th1 vs Th2 CD4 T cell response during infection determine outcome?

Answer 11

-Mycobacterium leprae can be cleared efficiently in patients with predominant Th1 response but progress to destructive form of leprosy when Th2 response dominates

Question 12

What is the primary role of Th17?

Answer 12

• recruit other immune cells (neutrophils) to site of infection
• stimulate production of anti-microbial peptides called defensins through secretion of IL-17 and IL-22

Question 13

How do intracellular bacteria attempt to evade immune response?

Answer 13

-produce proteins that allow escape from phagolysosome

Question 14

How do viruses evade immune system?

Answer 14

• inhibition of antigen processing
• production of cytokine receptor homologues
• production of immunosuppressive cytokines