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Vaccines > Chapter 2 Vaccine Immunology > Flashcards

Chapter 2 Vaccine Immunology Flashcards

1
Q

Describe overall how vaccines induce protection against disease.

A

They induce effector mechanisms capable of rapidly controlling replicating pathogens or inactivating their toxic components.

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2
Q

Name three (3) effector mechanisms induced by vaccines.

A
  1. Production of antibodies by B-cells
  2. Cytotoxic CD8+ T-cells
  3. CD4+ helper T-cells (Th cells)
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3
Q

Name five (5) types of helper T-cells.

A
  1. Th1 cells
  2. Th2 cells
  3. Th17 cells
  4. Tfh cells
  5. Treg cells
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4
Q

What type of antigen elicits a T-independent immune response?

A

Capsular polysaccharides.

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5
Q

What is the hallmark of a T-dependent antibody response?

A

Induction of higher affinity antibodies and immune memory.

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6
Q

Define adjuvant.

A

Any agent that increases the stimulation of the immune system through enhanced antigen presentation and/or costimulation signals.

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7
Q

What is the most common adjuvant used in today’s vaccines?

A

Aluminum salts.

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8
Q

Define antibody affinity.

A

Strength of the binding interaction between the antibody and a specific epitope at the surface of an antigen.

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9
Q

Define antibody avidity.

A

Sum of the epitope-specific affinities of an antibody for a given antigen.

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10
Q

What is the main processes underlying affinity maturation in B cells?

A

Somatic hypermutation and affinity-based selection.

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11
Q

Define antigen-presenting cell.

A

Any cell that :

  1. Captures antigens by endocytosis or phagocytosis
  2. Process them into small peptides
  3. Display them at their surface through MHC molecules
  4. Provide costimulation signals that synergistically activates T-cells
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12
Q

Name three (3) antigen-presenting cells.

A
  1. B cells
  2. Macrophages
  3. Dendritic cells (only ones capable of activating naïve T cells)
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13
Q

What three (3) main cytokines are secreted by Th1 cells?

A
  1. IL-2
  2. IFN-gamma
  3. TNF-beta
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14
Q

What cells of the immune system are supported by Th1 cells?

A
  1. Cytotoxic T cells
  2. Macrophages
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15
Q

What five (5) main cytokines are secreted by Th2 cells?

A
  1. IL-4
  2. IL-5
  3. IL-6
  4. IL-10
  5. IL-13
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16
Q

What cells of the immune system are supported by Th2 cells?

A

B lymphocytes.

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17
Q

What effector mechanism is directly induced by Th2 cells?

A

Extracellular antimicrobial functions, mainly against parasites.

18
Q

What four (4) main cytokines are secreted by Th17 cells?

A
  1. IL-17
  2. IL-21
  3. IL-22
  4. IL-26
19
Q

What is the main immune function of Th17 cells?

A

Defense against extracellular bacteria colonizing and/or invading exposed surfaces (mucosa, epithelia, skin).

20
Q

Define central memory T cells (T_CM).

A

Memory T cells that traffick through lymph nodes and that are ready to proliferate and generate a high number of effector cells in response to specific microbial peptides.

21
Q

What is the main function of dendritic cells?

A

Constantly patrol and sample their surroudings for pathogens.

22
Q

Define effector memory T cells.

A

Memory T cells that patrol the body to detect specific microbial peptides and that are capable of an immediate cytotoxic function.

23
Q

What are the four (4) main functions of Tfh cells?

A

Help follicular B lymphoctes to :

  1. Perform isotype switching
  2. Perform affinity maturation
  3. Undergo affinity-based selection
  4. Differentiate into plasmocytes or memory B cells
24
Q

Define isotype switching.

A

Switch of Ig surface expression and production by B cells from IgM to IgG, IgA or IgE that occurs during B-cell differentiation through DNA recombination.

25
Q

Describe how pattern recognition works.

A

Germline-encoded receptors detect conserved microbial pathogen-associated molecular patterns and trigger innate immune responses.

26
Q

What two (2) main cytokines are secreted by regulartory T cells?

A
  1. IL-10
  2. TGF-beta
27
Q

What are the three (3) main roles of Treg cells?

A
  1. Suppressing the activation of the immune system
  2. Maintaining immune homeostasis
  3. Mainting tolerance to self-antigens
28
Q

Define resident memory T cells.

A

Effector memory cells that reside in specific tissues and that confer an immediate line of defense against pathogens.

29
Q

Define somatic hypermutation.

A

Process that introduces random mutations in the variable region of the B-cell receptor at an extremely high rate during B-cell proliferation.

30
Q

Describe the four (4) main mechanisms of action of antibodies.

A
  1. Binding to enzymatic active sites of toxins or preventing their diffusion
  2. Neutralizing viral replication (e.g. preventing viral binding and entry into cells)
  3. Promoting opsonophagocytosis of extracellular bacteria
  4. Activating the complement cascade
31
Q

Describe the very first requirement to elicit an immune response to a vaccine.

A

Dendritic cells must provide sufficient danger signals to trigger an inflammatory reaction.

32
Q

Why is a 3-week interval between vaccine doses required?

A

To avoid competition between successive waves of primary responses.

33
Q

What are the three (3) main events of the germinal center reaction.

A
  1. Massive clonal proliferation of B cells
  2. Ig class-switch recombination
  3. Maturation of affinity through somatic hypermutation
34
Q

How long does the germinal center reaction usually take to produce high affinity antibodies in circulating blood?

A

Between 10 and 14 days.

35
Q

What are the three (3) main types of immune reactions to vaccines?

A
  1. Extra-follicular reaction
  2. Germinal center reaction
  3. T-independent B-cell reaction to polysaccharide antigens
36
Q

What are the five (5) hallmarks of a memory B-cell immune response?

A
  1. Memory B cells are generated only during T-dependent primary germinal center responses.
  2. Memory B cells are resting cells that do not produce antibodies.
  3. Memory B cells undergo affinity maturation during 4 to 6 months.
  4. Memory B cells can differentiate within days into antibody-secreting plasma cells upon reexposure.
  5. Antibodies generated by plasma cells issued from memory B cells have much higher affinity than those produced during primary responses.
37
Q

Why are secondary responses to live attenuated vaccines so small?

A

Because rapid secretion of antibodies neutralize the attenuated virus before it can replicate.

38
Q

What are the five (5) main determinants of secondary B cell responses?

A
  1. Postprimary antibody titers
  2. Residual antibodies at boosting
  3. Lower antigen dose at priming
  4. Longer intervals before boosting
  5. Higher antigen dose at boosting
39
Q

What are the three (3) main phenotypes of memory T cells?

A
  1. Central memory T cells
  2. Effector memory T cells
  3. Tissue resident memory T cells
40
Q

What are the four (4) main determinants of T cell memory response?

A
  1. Frequency of memory T cells
  2. Phenotype of memory T cells
  3. Persistence of memory T cells
  4. Localization of memory T cells
41
Q

What are the seven (7) main limitations of vaccine response in infants?

A
  1. Limited magnitude of antibody response to polysaccharide antigens
  2. Limited magnitude of antibody response to peptide antigens
  3. Short persistence of antibody response to peptide antigens
  4. Shorter duration of immune memory (possibly)
  5. Limited IFN-gamma responses
  6. Limited CD8+ T-cell responses
  7. Influence of maternal antibodies
42
Q

What are the six (6) main limitations of vaccine response in elderly people?

A
  1. Limited magnitude of antibody response to polysaccharide antigens
  2. Limited magnitude of antibody response to peptide antigens
  3. Limited quality of antibodies (affinity and isotype)
  4. Short persistence of antibody response to peptide antigens
  5. Limited induction of CD4+ and CD8+ responses
  6. Limited persistence of CD4+ response

Vaccines (9 decks)

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