Immuno 13

Question 1

Antigenic Variation

Answer 1

Alteration of epitopes displayed by a pathogen that make epitopes unrecognizable by an existing immune response

Question 2

Antigenic Drift

Answer 2

intro of point mut. that results in minor alterations of antigenicity of a particular protein

Question 3

Antigenic Shift

Answer 3

reassortment of genes that results in major changes in antigenicity of given protein

Question 4

Latency

Answer 4

State in life cycle of viruses during which they do not replicate and remain hidden from immune system

Question 5

Superantigen

Answer 5

molecules that stimulate subset of CD4 T Cells by simultaneously binding the MHC Class II mculs and beta-chain of TCR. These are not specific interactions

Question 6

What are the 3 ways antigenic variation occur?

Answer 6

Having multiple serotypes
Antigenic Drift
Antigenic Shift

Question 7

What is a serotype?

Answer 7

The distinct polysaccharide capsule of an antigen. They allow the same antigen to cause the same disease multiple times in an individual.

Question 8

Example of Serotype Bacteria

Answer 8

S. pneumoniae

Question 9

Example of disease that uses Antigenic Shift and Antigenic Drift

Answer 9

Flu

Question 10

How does antigenic drift in flu affect a population?

Answer 10

There is significant cross-reactivity with Ab and T cells from the old strains. Thus, part of the population will be immune to new strand, and the symptoms are typically mild.

Question 11

How does antigenic shift in flue affect a population?

Answer 11

It arises from reassortment of segmented negative-strand RNA genome. Leads to major changes in humagglutinin on surface of virus. Resulting virus is not recognized by old Abs. More people are susceptible, and symptoms more severe

Question 12

Variant-specific Glycoprotein

Answer 12

a single type of glycoprotein that coats trypanosomes. Each trypanosome has appx. 1000 different VSG genes, using cassete system to create variability.

Question 13

How does sleeping sickness work stay in the system?

Answer 13

The body produces Abs against a certain VSG. However, some parasites still escape immune response because they express different VSGs, leading to a recurrence of the disease. Continuous immune response can damage host tissue over time, including neuro damage leading to coma.

Question 14

Explain latency in Herpes Simplex Virus

Answer 14

Infects epithelia, then spreads to neurons. Effective immune response clears epithelial infxn, but virus persists in latent phase in neurons by integrating into host DNA. Reactivated, travels along sensory neurons and reinfects epithelial tissues.

Question 15

Two ways sensory neurons remain infected with viruses

Answer 15

1. Virus is latent, so very few antigen peptides are presented to CTLs.
2. Neurons express low levels of MHC I mculs, preventing CTL recogn. Impt cause neurons cannot be regenerated.

Question 16

Three examples of latent viruses

Answer 16

varicella zoster (chicken pox)
Epstein-Barr Virus
Herpes Simplex Virus

Question 17

Four Ways Viruses Avoid Control Immune Responses

Answer 17

1. capturing cellular genes for cytokines (receptors)
2. making complement-regulatory proteins
3. inhibit MHC I mcul synthe or assembly
4. Tuberculosis prevents phagolysosome forming once taken up by macrophages.

Question 18

How do superantigens affect immune response?

Answer 18

Induce massive production of cytokines by CD4 cells. Initiates immunosuppression and systemic toxicity.

Question 19

How do superantigens work?

Answer 19

Simultaneously bind to the MHC Class II mculs and V-beta region of the TCR. Each can only stimulate 2-20% of all T cells. Non-specific reaction, through massive cytokine production.

Question 20

Two major forms of Leprosy

Answer 20

1. Lepromatous Leprosy

2. Tuberculoid Leprosy

Question 21

Describe Lepromatous Leprosy

Answer 21

cell-mediate immunity is severely depressed, and infxn isn’t controlled. low or absent T cell response. Replicated freely in macrophages, leaving the host in an anergic state.

Question 22

Describe Tuberculoid Leprosy

Answer 22

cell-mediated immunity with macrophage activation, which controls infxn but d/n eliminate it. Bacteria is present at low levels. Granulomas and local inflammation are observed.Normal T Cell response.

Question 23

What is seroconversion?

Answer 23

The phase of an immune response when antigen-specific antibody production is 1st detectable.

Question 24

Which T cell is profoundly decreased in HIV?

Answer 24

CD4 T Cells

Question 25

How does HIV cause low CD4 T Cell levels?

Answer 25

The envelope protein of HIV binds to CD4 mculs. Once bound, it must interact with co-receptor on host cell to gain entry into cell. Following initial infection, HIV replicated rapidly in blood, causing a marked reduction in CD4 T cell numbers.

Question 26

When does seroconversion occur in HIV?

Answer 26

2-6 weeks after infection

Question 27

What does latency of HIV correspond with?

Answer 27

Latency (asymptomatic) begins about the same time as seroconversion begins. Lasts for 10 years.

Question 28

What must drop in concentration for symptomatic AIDS to occur?

Answer 28

T cell levels

Question 29

How does HIV evade immune responses and drug therapies?

Answer 29

Using antigenic variation caused by an inaccurate reverse transcriptase, there are many point mutations during every replicative cycle.

Also, antiviral drugs lower the viral amt. but mutants eventually repopulate.

Question 30

How long does resistance take to develop to Zidovudine (AZT)?

Answer 30

A reverse transcriptase inhibitor that takes makes to acquire immunity to because it would require several point mutations to develop in reverse transcriptase gene.