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MIIM30002 > Lecture 28: Immune Memory > Flashcards

Lecture 28: Immune Memory Flashcards

1
Q

What is the basis of vaccination (and the reason why vaccines work)?

A

immunological memory

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2
Q

How do naive and memory cells differ?

A

differences in frequency (10^4 - 10^5 in the naive repertoire and 10^2 - 10^3 in the memory repertoire)
differences in their function / phenotype

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3
Q

Which antibodies do memory B cells produce?

A

IgG and IgA

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4
Q

What are the fate decisions of B cells?

A

low affinity IgM secretion
isotype switch, low affinity IgG
IgG secretion, high affinity
memory B cell

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5
Q

What are memory B cells generated in response to?

A

T-dependent antigens

generated during germinal centre reaction

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6
Q

What is the role of long lived plasma cells?

A

direct protection

antibody production is antigen independent

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7
Q

Where do long lived plasma cells migrate to?

A

the bone-marrow

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8
Q

Where do memory B cells migrate to?

A

the spleen / LN

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9
Q

What is the role of memory B cells?

A

required for immune protection when serum antibody not present at high enough concentration

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10
Q

Why are memory B cells better than naive B cells?

A

present in higher numbers than naive B cells
respond to reactivation faster
have undergone affinity maturation -> produce higher quality antibody

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11
Q

How do almost all clinically effective vaccines act?

A

via antibody-mediated immunity

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12
Q

How do pathogens such as HIV, influenza and TB escape humoral immunity?

A

by the rapid variation of antigens and / or intracellular localisation (T cell-mediated immunity required for control)

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13
Q

What are the characteristics of memory T cells?

A

increased precursor frequency (1000x) compared to naive cells
different phenotype
rapid effector function
long-lived

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14
Q

What do naive T cells require for survival?

A

need self-MHC molecules and IL-7

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15
Q

What do memory T cells require for survival?

A

do not need MHC expression

need IL-15 for survival (+IL-7)

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16
Q

What are the different types of memory T cells?

A

effector memory T cells, central memory T cells and resident memory T cells

17
Q

What are the different models by which memory T cells are generated?

A

separate precursor model, asymmetric fate model, decreasing potential model and signal strength model

18
Q

What does T-bet influence?

A

the formation of short-lived effector cells (90%)

19
Q

What does eomes influence?

A

the formation of memory precursor cells (10%)

20
Q

What do long-lived memory cells express?

A

IL-7R+ KLRG1-

21
Q

What do memory T cells depend on?

A

IL-15

22
Q

What are CD4 T cells required for?

A

generation of CD8 T cell memory

23
Q

Why are CD4 T cells required for CD8 T cell memory?

A

involved in dendritic cell licencing / activation -> co-stimulation, cytokines
provision of IL-2 signals

24
Q

Why is CD4+ T cell memory more complex?

A

because of the diversity of effector cells formed

numbers decline faster than CD8+ T cells post infection

25
Q

What is the localisation of central memory T cells?

A

blood and lymphoid tissues e.g. lymph nodes, spleen, bone marrow

26
Q

What are the functional properties of central memory T cells?

A

increased proliferative potential, increased IL-2, increased recirculation and decreased effector function

27
Q

Where are effector memory T cells localised?

A

blood and nonlymphoid tissues e.g. gut, liver, skin, lungs

28
Q

What are the functional properties of effector memory T cells?

A

decreased proliferative potential, decreased IL-2, increased recirculation and increased effector function

29
Q

Which T cells are lost over time?

A

effector memory T cells

30
Q

What is the localisation of tissue-resident memory T cells?

A

mainly tissues: gut, skin, lung, glands, brain, thymus, lymph nodes
high frequency at sites of previous infection

31
Q

What are the functional properties of tissue-resident memory T cells?

A

decreased IL-2, no recirculation and increased effector function

32
Q

What is the evidence of tissue-resident memory T cells being non-recirculating cells?

A

tissue-transplantation and cell depletion

33
Q

How were tissue-resident memory T cells missed?

A

studies often limited to human blood

previously thought memory T cells in the tissues and blood were the same

34
Q

What does location of memory T cell dictate?

A

rapidity of memory T cell protection

35
Q

What do high numbers of T resident memory cells correlate with?

A

subclinical herpes virus reactivation

patients that control HIV infection

36
Q

What do T resident memory cells provide?

A

immunity against re-infection

are present at sites of previous infection

37
Q

What do patients with more T resident memory cells have?

A

better outcomes against cancer

force cancer into a state of dormancy

MIIM30002 (25 decks)

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