Vaccinations (1/14)

Question 1

What are the similarities and differences between Naive T cells and Memory T cells?

Answer 1

Memory T cells don’t require CD28 (2nd receptor) to activate

Memory T cells can be activated by a broader array of antigen presenting cells (DC, B cells, ET cells, macrophages) whereas naive T cells can only be activated by dendritic cells

Memory T cells can produce many types of cytokines whereas naive T cells only make IL-2

Question 2

Where are memory T cells found in the body?

Answer 2

Everywhere- in all major tissues in your body– lung, liver, skin, intestine – act as important sentinels

Naive T cells are mostly in spleen/marrow

When you’re an adult, most of your T cells are memory T cells

Question 3

What are neutralizing antibodies? How are they involved in protective immunity?

Answer 3

They are antibodies that bind to surface strucutres of viruses/bacteria

These are also the structures that are highly mutated among different strains of bacteria, so vaccination against one strain might not protect you against other strains (although cowpox innoculation protects against smallpox)

Question 4

What are the mechanisms of T cell mediated protection?

Answer 4

Cytoxic T cells: Fas binding to virus infected cell leads to secretion of cytotoxins for exocytosis & cytokines - tons of IFN-gamma + LT

Th1 cells: bind macrophages that contain bacteria, activate killing response, secrete lots of cytokines

Th2 cells: bind B cells to activate creation of lots of antibodies, secret tons of cytokines

Question 5

What are the 3 main strategies for vaccines?

Answer 5

1. Killed bacteria/inactivated virus
2. Live-attenuated viruses
3. Subunit vaccines: i.e. toxin protein, viral protein subunits

Question 6

How is an attenuated virus made?

Answer 6

1. Isolate pathogenic virus from patient & grow in human cultured cells
2. Infect the cultured virus into monkey cells
3. The virus acquires many mutations that allows it to grow well in monkey cells
4. Now the virus no longer grows well in human cells & can be used as vaccine

Question 7

What are adjuvants?

Answer 7

Something that act as delivery systems to enhance an immune response against antigen in vaccines i.e. provide necessary second signal or stimulate innate immunity

This allows antigen sparing when you need many doses

Examples: alum enhances uptake by APC, active inflammasome, stimulates Th2 mediated responses

water/oil emulsion: can act as an irritant

Question 8

Why is it difficult/impossible to make a vaccine for malaria?

Answer 8

There is no memory response to malaria, even in those who have been infected

Question 9

What are 3 major challenges for vaccines?

Answer 9

1. pathogens mutate at high rates i.e. influenze –> problem bc you can make a vaccine but not anticipate a new strand, so the vaccine won’t include the new strain
2. chronic viral infections establish latency
3. cancer: tumors evade immune responses

Question 10

Why is it hard for vaccines to work against chronic infections?

Answer 10

Chronic infection turns on the negative regulators of the T cell response –> lots of chronic viruses are able to persist bc T cells are turned off

Antiviral therapies are the best treatment

Question 11

Do vaccines cause disease or worsen clinical outcome to pathogen exposure?

Answer 11

This happened in early polio vaccination- some people got polio from the attenuated strain