Test 1 - Host Response to Viral Infection (10)

Question 1

What are defensins and where are they found?

Answer 1

Host defense peptides with antiviral activity found in the GI tract.

Question 2

What are the innate defenses found in the Respiratory tract?

Answer 2

1. Mucociliary blanket
2. Temperature gradient

Question 3

TRUE/FALSE.

NK cells are antigen specific.

Answer 3

FALSE.

They are activated through surface receptors (inhibitory signal is stronger than activating signal)

Question 4

PAMPs bind to _______.

Answer 4

Pattern Recognition receptors

Question 5

What kind of viruses are stronger inducers of interferons?

Answer 5

RNA viruses

Question 6

Explain the process of gene silencing.

Answer 6

• Cells utilize small, interfering, RNA molecules (RNAi) to silence genes as a means of regulating normal developmental and physiological processes, and potentially to interfere with virus replication.
•  Production of RNAi initiates formation of the RNA-silencing complex that includes an endonuclease that degrades those mRNAs with a sequence that is complementary to that of the RNAi.
•  Cells can utilize this mechanism to disrupt virus replication through the production of RNAi that are complementary to specific viral genes.

Question 7

Define granulocytosis.

Answer 7

The presence in peripheral blood of an increased number of granulocytes, i.e. Neutrophils, eosinophils, basophils, mast cells.

Question 8

Antibodies are directed against what?

Answer 8

Virus capsid and envelope, proteins

Question 9

What effects can Antibodies have on viruses?

Answer 9

Neutralization

Opsonization

Clumping (immunocomplex formation)

Activation of the complement (opsonization, chemotaxis, lysis, agglutination)

Antibody-dependent cell-mediated cytotoxicity

Question 10

How do viruses evade the immune system?

Answer 10

1. Antigenic plasticity: Rapid changes in the structure of the viral antigen. May be the result of mutation, reassortment or recombination.
2. Antigenic multiplicity: Antigenic variants with little or no cross-reactivity.
3. Negative cytokine regulation
4. Down-regulation of MHC class I pathway
5. Inihibition of Complement
6. Evasion of neutralizing antibodies
7. Latency- integration into host genome
8. Inhibiton of apoptosis