Immunology of Vaccination

Question 1

Define vaccination

Answer 1

Deliberate induction of an adaptive immune response to a pathogen by injecting a vaccine- a killed/attenuated form of the pathogen

Question 2

Define immunisation

Answer 2

Deliberate provocation of an adaptive immune response by introducing an antigen into the body

Question 3

What is meant by complete protection?

Answer 3

Lifelong immunity

Question 4

What is meant by partial protection?

Answer 4

Requires boosters (some microbes/vaccines do not induce a strong enough immune response)

Question 5

How is memory established for specific pathogens?

Answer 5

Generation of memory T and B cells

Question 6

What is active immunisation?

Answer 6

Administration of micro-organisms or toxoid/purified antigen etc. to invoke an immune response matching that of natural infection, usually present little or no risk to recipient

Question 7

What is passive immunisation?

Answer 7

Administration of performed antibody to recipient for prevention of infection (temporary)

Question 8

Describe passive vaccination

Answer 8

• Usually very available
• Short-lived and temporary
• Given IM- contain antibody aggregates and other serum products- can activate complement if given IV- anaphylaxis

Question 9

What are the sources of passive vaccination?

Answer 9

• Almost all blood products
• Homologous pooled human antibody
• Homologous human hyperimmune globulin (Rabies, CMV)
• Heterologous hyperimmune serum (anti-toxin- produced in animals)
• Transplacental- important in infancy

Question 10

Describe active vaccination

Answer 10

• Long lived- similar to natural infection without risk of disease
• Live attenutated
• Inactivates
• Detoxified endotoxin (toxoid)

Question 11

Describe live attenuated vaccine

Answer 11

• Attenuated form of natural virus/bacterium
• Must replicate
• Immune response similar to natural- few doses needed
• Can induce severe reactions
• Requires careful storage

Question 12

Describe inactivated vaccine

Answer 12

• Cannot replicate
• Generally not as effective as live vaccines
• Requires multiple doses
• Mostly humeral (B cell antibody) responses
• Antibody titres reduce over time

Question 13

What are the different types of inactivated vaccine?

Answer 13

• Whole- entire organism used
• Split- detergent lysed
• Subunit/ recombinant/ polysaccharide/ conjugate- purification of most immunogenic antigens

Question 14

What is the tetanus vaccine directed against?

Answer 14

Tetanus toxoid

Question 15

How are B and T cells activated with the tetanus vaccine?

Answer 15

• Dendritic cells present toxoid peptide antigen to CD4 T cells in lymph node
• Activates T Helper cells

Question 16

How are toxoid specific antibodies generated with the tetanus vaccine?

Answer 16

• Activated B cells differentiate into plasma cells
• Secrete toxoid-specific antibodies
• Generate B cell memory

Question 17

Why does the Tetanus vaccine require multiple doses?

Answer 17

• Not very immunogenic

- Only activates humeral response and a weak T cell response

Question 18

What does the tetanus vaccine need to induce an effective response?

Answer 18

Adjuvant- alum

Question 19

What type of vaccine is the MMR vaccine?

Answer 19

Live attenuated (trivalent)

Question 20

How are T and B cells activates in the MMR vaccine?

Answer 20

• Dendritic cells present viral peptide antigen (bound to MHC 1 and 2) to T cells
• Activated CD4 helper and CD8 cytotoxic T cells- unlike tetanus
• Binding to viral antigen by BcR activated B cells

Question 21

How is the adaptive response activated with the MMR vaccine?

Answer 21

• T cells traffic to site of infection

- Virus-specific antibodies migrate to infection site

Question 22

Why is the MMR vaccine effective?

Answer 22

Induces protective immunity- requires a few doses

Question 23

What is the MMR vaccine not suitable for?

Answer 23

Immunocompromised