Chapter 4

Question 1

What can viruses do?

Answer 1

• Viruses can produce proteins that actively block an aspect of the immune response.
• Inhibit other cytokine signalling
• Inhibit apoptosis as an immune response
• Subvert NK cell killing
• Affect antigen processing and presentation
• Viruses have mechanisms to down-regulate MHC-I expression.

Question 2

What does MHC-1 do?

Answer 2

• presents viral antigens on the cell surface for killer T cells to recognize and kill the infected cell.

Question 3

Herpesviruses can

Answer 3

-down regulate MHC-1

interfere with peptide loading into MHC-1

Produce an analogue of IL-10 to block cytokine synthesis (EBV)

Interfere with MHC-II expression

Block apoptosis (KSV)

Question 4

what does HIV do?

Answer 4

Targets and infects CD4+ T cells - to disable their IR

HIV proteinase cleaves Bcl-2 to encourage cell death

Nef and Tat decrease MHC-I expression.

Weakening CD8+ T cell responses

Question 5

what are the four steps of passive immune evasion?

Answer 5

1. Evading the immune response without producing a specific protein to block a specific mechanism
2. Molecular mimicry
3. Latency
4. Bury antigenic or vitally important protein structures

Question 6

genetic variability can?

Answer 6

vary between individual hosts and can affect virus replication

and can make a host more or less susceptible to viral infection

Question 7

what surface molecule presents cytoplasmic antigens?

Answer 7

MHC class 1

Question 8

What type of T cell recognizes antigens presented on MHC class II?

Answer 8

CD4+ T cell

Question 9

MHC class I presents cytoplasmic (viral) antigens to

Answer 9

CD8+ T cells

Question 10

APCs recognize

Answer 10

viruses as foreign harmful pathogens, intentionally ”eat” the viruses
• APCs are not infected.
• Engulf the viruses inside the endosome, break them apart, and present viral antigens on MHC II molecules on the cell surface
• Extracellular viruses
• Endosomal pathway