Lecture 12 (6B) - Immunological Memory Flashcards

1
Q

Immunological memory

A

the ability of the immune system to respond quicker and better to pathogens that have been encountered previously

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2
Q

Damage and infection stimulates

A

inflammation

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3
Q

Inflammation

A

damaged tissues make proinflammatory cytokines
• macrophages in
• TNFα, IL-1, IL-6, IL-8
• the wound bleeds to wash out foreign bodies
• resident macrophages and the injured tissues initiate an inflammatory response

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4
Q

Inflammation first drives

A
the innate immune response
• clot forms to seal the wound
• macrophages
• NK cells
• neutrophils
• fluid enters the site
• IgM

keep under control until adaptive

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5
Q

Dendritic cells initiate

A

adaptive immunity
• DC gets pieces of pathogens and
• have TLR/pathogen recognition receptors on surface so can respond /recognize pathogens
• acts as danger signal
• upregulates B7 and CD40 on DC -> signal T cells to proliferate

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6
Q

Immature DC –> Mature DC

A
  • in the tissues is scanning, finds danger signals
  • maturation on meeting a microbial challenge (danger signals)
  • becomes a mature dendritic cell that goes to the lymphatics and lymph nodes
  • upregulates B7 and CD40 - the signal for the T cells to proliferate
  • when mature starts chopping up bits of proteins , upregulates MHC on surface, puts protein in MHC, turns on B7 and CD40, goes to lymph nodes (primed DC)
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7
Q

Dendritic cells go to the lymph nodes

A

activates naive T cells - passes protein to other DC, they interact with naive T cells - find one that recognizes the MHC+peptide
• in through afferent lymphatics
• activate/prime T cells that proliferate
• TH1 helper T cells and cytotoxic T cells leave through efferent to the site of infection =

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8
Q

Cell-mediated immunity

A

clones of T cells leave lymph node back to site of problem

  • CD4 or CD8
  • CD8 kill directly - with perforin and granzymes
  • Th1 cells support cytotoxic T cells and macrophages = cell mediated response, good for getting rid of pathogens that infect cells
  • Th2 cells
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9
Q

Humoral immunity

A

Th2 cells help B cells make antibodies which are good at catching big pathogens

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10
Q

B cells become plasma cells

A
which produce huge amounts of diverse antibodies
• IgM - makes this first, low affinitiy
• IgG - blood
• IgE - mast cells, allergies
• IgA - mucosal

make a lot of IgG to send to site of infection

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11
Q

A fraction of the activated T and B cells become

A

memory cells and provide long-lasting immunity to that infection

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12
Q

A fraction of the activated T and B cells become memory cells and

A

provide long-lasting immunity to that infection
• cytotoxic T cells
• helper T cells
• B cells
- in an active immune response, there’s lots
- lots are left after an immune response, but not enough storage, so just want to keep the useful ones

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13
Q

After an active immune response

A

effector cells are stored for rapid deployment if infection re-occurs
• memory cytotoxic T cells
• memory helper T cells
• memory B cells

  • still have more than the original, faster
  • pathogens would also have to proliferate to keep up, but can’t –> can’t beat memory
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14
Q

Immunological memory can be maintained WITHOUT

A

continued exposure to the pathogen

• it is maintained by long-lived antigen-specific lymphocyte that persist for many years

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15
Q

Immunological memory is maintained by

A

long-lived antigen-specific lymphocytes that persist for many years
• can be maintained without continued exposure to the pathogen

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16
Q

Demonstrating immunological memory

A
  1. infect animal with virus
  2. animal survives
  3. 1 month later take the white blood cells
  4. transfer lymphocytes - T and B cells - to a mouse that has never seen the virus
  5. it is protected so when challenged with the virus, it doesn’t develop disease
17
Q

Spanish flu (1918-1919)

A

• more recorded deaths than any other infectious disease ever
• 25 million people (estimates up to 100 million)
• most people who died were
- very young (immune system not fully developed)
- very old (immune system deteriorates)
• people who survived the russian flu had active memory for the spanish flu

18
Q

B cell memory

A

• 100-fold more antigen-specific memory B cells than naive B cells
• antibody produced with higher affinity for antigen
(high affinity of antibody, high somatic hypermutation)
• higher MHC-II and increased B7.1 and B7.2

19
Q

Higher affinity antibodies in

A

secondary immune response
• primary infection - made different antibodies, some with low, medium, or high affinity
• secondary infection - antibodies made from primary still there, but low affinity antibodies are outcompeted (B cell that makes it won’t make much)
• tertiary infection - almost no antibodies with low affinity, make less of medium affinity, those with high affinity are boosted (B cell selected for)
–B cells will mutate to make higher affinity
– B cells improve affinity of antibody

20
Q

Somatic hypermutation in the germinal centers of lymph nodes

A

the process of directed mutation to the variable region of the antibody molecule, followed by selection for high affinity antibody/antigen interactions results in the progressive improvement of antibody affinities

21
Q

Memory T cells

A

• increased frequency of cells (100-1000 fold higher)
• increased survival characteristics eg increase in Bcl-2
• can be re-stimulated much more easily - the requirement for costimulation is much reduced
(originally hard to activate because only want proinflammatory when super necessary)
• rapidly proliferated and rapidly produce effector cytokines (eg IFN-γ)

22
Q

Memory t cells can be identified by their

A
surface molecules
• CD44
• CD45RO
• DD45RA
• CD26L - some
• CCR7 - some
• CD69 - none
• Bcl-2
• interferon-γ
23
Q

2 types of memory T cells

for both CD4 and CD8

A
  • effector memory T cells

* central memory T cells

24
Q

Effector memory T cells

A
  • rapidly mature to secrete IFN-γ, IL-4 and IL-5
  • lack the LN-homing receptor CCR7
  • have tissue-homing receptors (CCR5) and inflammatory cytokine receptors

TISSUE MEMORY CELLS
RAPID-RESPONSE UNIT

  • need CCR7 to go to lymph node
  • no CCR7 = goes to tissue so there when an infection comes to tissue

• CCR5 = gut homing receptor

  • when activated don’t proliferate but send out cytokines
  • rapid response unit

have inflammatory cytokine receptors, TCR, CCR5

25
Q

Central memory T cells

A

• express CCR7 and reside in secondary lymphoid tissue
- CCR7 = go to lymph nodes
• expand into effector cells rapidly and in large numbers

PROVIDE REINFORCEMENTS IN LARGE NUMBERS
• help effector memory T cells

have CCR7, TCR, L-selectin