Memory and Vaccinations

Question 1

What is the function of a memory B cell?

Answer 1

The memory B cells remember the pathogen and are specific to that pathogen. Meaning there is faster antibody production if the pathogen returns

Question 2

What are the properties of a memory B cell?

Answer 2

Produce higher affinity antibody than plasma cells
Produce class-switched antibodies
Produce antibodies quickly
Have high levels of MHC and costimulatory molecules to attract T cell help

Question 3

What is a follicular B cell?

Answer 3

A type of B cell that resides in primary and secondary lymphatic follicles (including germinal centers) of the secondary and tertiary lymphoid organs-e.g spleen, lymph nodes

Question 4

How is a memory B cell produced?

Answer 4

• Follicular B cell receives T cell signals causing it to proliferate
• They move into a germinal center where they undergo somatic hypermutation and proliferation, causing class switching recombination
• Go through affinity selection and if beneficial receive survival signals from T cell
• Differentiate into a memory cell (instead of a long-lived plasma cell)

Question 5

How are memory T cells produced?

Answer 5

• Naive T cells activated by dendritic cells in lymph nodes
• Naive T cells differentiate to adopt different affector phenotypes
• Some effector cells become memory cells
• Most effector cells die by apoptosis
• But memory cells survive as they respond to survival signals by cytokines ( IL-7 and/or IL-15)

Question 6

What are the 2 types of memory T cell?

Answer 6

Effector memory T cell

Central memory T cell

Question 7

What are effector memory T cells and what is is their function?

Answer 7

• Live in tissues not lymph nodes
• Immediate expansion on infection
• Have receptors for inflammatory chemokines so can be recruited to inflammation rapidly
• Produce IFNy, IL-4 or IL-5 quickly

Question 8

What are central memory T cells and what is their function?

Answer 8

• Behave more like naive cells
• Live in the lymph nodes
• Need antigen presenting to them again
• Long lived precursors that take longer to respond

Question 9

How can the innate immune system alos show ‘memory’?

Answer 9

Innate memory is reffered to as trained immunty
Trained immunity involves epigenetic changes, metabolic changes and improved effector functions to improve the innate immune response

Question 10

In what situation would a vaccine not provide immunity?

Answer 10

If the antigen in the vaccine is simply cleared by the innnate immune system the vaccine wont work
(cant trigger adapative immunity cells)

Question 11

What does a vaccine aim to trigger?

Answer 11

Trigger B cell activation and antibody production

The best vaccines also trigger T cell immunity- essential for viral infection

Question 12

What are the requirements for a vaccine?

Answer 12

Safe- must not itself cause illness or death
Protective- must protect against all illness caused by the specific pathogen
Gives sustained protection

Question 13

What are the practical considerations to a vaccine?

Answer 13

• Low cost per dose
• Biological stability
• Ease of administration
• Low side effects

Question 14

What are the different types of vaccines?

Answer 14

Live attenuated pathogen (typically viral)
Inactive pathogen
Conjugated
Subunit or toxoid

Question 15

What is the first method of producing a live attenuated pathogen vaccine (Rotavirus and MMR) ?

Answer 15

1st way:

• Pathogen isolated and cultered in human cells
• Used to infect an animal’s cells (usually monkey)
• Virus aquired mutations to allow it to grow well in monkey cells
• These mutations reduce its ability to grow in human cells when used as a vaccine

Question 16

What is the second method of producing a live attenuated pathogen vaccine (Rotavirus and MMR)?

Answer 16

2nd way:

• Isolate the pathogenic virus
• Identify the virulence genes
• Mutate OR delete the virulence genes to attenuate the virus

Question 17

What are the advantages and disadvantages to live attenuated pathogen vaccines?

Answer 17

Advantages:
-Immune recognition at multiple life cycle stages
-Long lasting immunity including T cell mediated effects
Disadvantages:
-Theoretically could revert to a pathogenic strain
-May act as an opportunistic pathogen for immunocompromised people
-Need special storage conditions

Question 18

What is the method to produce an inactive pathogen vaccine (Flu and Polio)?

Answer 18

• Isolate the live pathogenic organism
• Inactiavte the pathogen with heat or formaldehyde
• Pathogen is structurally intact but inactive to cannot replicate in the body

Question 19

What are advantages and disadvantages to an inactive pathogen vaccine?

Answer 19

Advantages:
-Pathogen cant replicate in body (non-pathogenic)
-Safe to use in immunocomprimised people
-Easily stored and transported
Disadvantges:
-Less effective than live vaccines- often need booster shots
-Dont include CD8 T cell response or mucosal immunity
-May produce pathogenic strain if not inactivated properly

Question 20

What are conjugate vacicnes?

Answer 20

Combine an antigen recognised by the B cell (e.g a polysaccharide) and a second antigen that will induce T cell help (e.g a toxoid)

Question 21

What is the immune response in the presence of a conjugate vaccine (Meningitis C)?

Answer 21

• B cell recognises the polysaccharide and takes up the whole vaccine molecule. It presents peptides of this and the toxoid on MHCII
• T cell recognises the toxoid being presented by the B cell and provides stimulation to cause B cell activation and class switching
• B cell produces antibodies to the polysaccharide that its receptor recognised and develops a memory response

Question 22

What are the advantages and disadvantges of conjugate vaccines?

Answer 22

Advantages:
-Creates a complete adaptive immune response involving CD4 T cells
-Dont use whole pathogens so cant cause disease
-Can be used in very young children
Disadvantages:
-Expensive to produce
-Dont include CD8 T cell response of effective mucosal immunity
-Need to be engineered to include lots of antigens to be sure a response to all pathogenic strains

Question 23

What is the method of making toxoid vaccines (Tetanus)?

Answer 23

• Some bacteria exert their hramful affects through toxin production
• Toxins are purified from the bacteria and inactivated
• Now reffered to a toxoids, and can induce the imune system to produce antibodies against the toxin without causing disease

Question 24

What is the method of making subunit vaccines (Whooping cough)?

Answer 24

• Pathogen bacteria is isloated
• The specific protein from the organism that causes the immune repsonse is isolated
• This protein is used in a vaccine to stimulate dendritic cells to take up and present the antigen

Question 25

What are the advantages and disadvantages of toxoid and subunit vaccines?

Answer 25

Advantages:
-Very safe (no pathgen so no infection)
-Easily stored and transported
Disadvantages:
-Less effective at inducing a long lasting immunity
-Dont induce a CD8 T cell response or effective mucosal immunity
-Need to be engineered to include lots of antigens to be sure a response to all pathogenic strains

Question 26

What are adjuvants?

Answer 26

Compounds that are mixed with the antigen or pathogen to: (e.g alum, bacteria cell wall components)

• enhance immunogenicity by giving a danger signal
• reduce the amount of antigen needed
• Aid delivery at the mucosa