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IMED2001 > The induced response to infection (1) > Flashcards

The induced response to infection (1) Flashcards

1
Q

What do cellular receptors of innate immunity do?

A

They distinguish ‘non-self’ from ‘self’

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2
Q

What do macrophages carry?

A

A battery of phagocytic and signalling receptors

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3
Q

What do toll-like receptors do?

A

Sense presence of 4 main groups of pathogenic microorganisms

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4
Q

What receptor recognises LPS?

A

TLR4

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5
Q

What does recognition of LPS by TLR4 do to macrophages?

A

Changes macrophage gene expression

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6
Q

What does genetic variation in TLR do?

A

Associated with resistance or susceptibility to disease

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7
Q

What happens when resident macrophages are activated?

A

A state of inflammation is initiated at site of infection

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8
Q

How do inflammasomes amplify innate immune system?

A

They increase production of IL-1beta

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9
Q

Which cells are first effector cells recruited to sites of infection?

A

Neutrophils

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10
Q

What do inflammatory cytokines do?

A

They recruit neutrophils from blood to infected tissue

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11
Q

What happens to neutrophils after they consume pathogens?

A

They destroy themselves and release cytokines

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12
Q

What do inflammatory cytokines do?

A

They raise body temperature, activate liver to make acute-phase response

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13
Q

How many phases to human immune response?

A

3

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14
Q

What happens during the immediate innate immune response?

A

Pathogen invades tissue and proliferates.

Pathogen is recognized by preformed soluble effector molecules and resident effector cells in the infected tissue

Pathogen is either eliminated or the induced innate response is triggered

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15
Q

How long is the immediate innate immune response?

A

0 - 4 hours

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16
Q

What happens during the induced immune response?

A

Pathogen invades tissue and proliferates

Activation of cells resident in the infected tissue. Recruitment of effector cells to the infected tissue. Inflammation, fever, the acute phase response.

Soluble effector molecules and effector cells recruited to infected tissue recognize and attack pathogen.

Pathogen is either eliminated or survives and instigates the adaptive immune response

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17
Q

What are innate recognition receptors that recognize pathogens?

A

Pathogen Recognition Receptors (PRRs)

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18
Q

Which cells express PRRs?

A

Macrophages, NK cells, and other cells of innate immunity

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19
Q

What do PRRs recognize?

A

Carbohydrates, lipids, proteins nucleic acids typically found on pathogenic surfaces

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20
Q

How do innate immune cells recognize self and non-self cells?

A

Pathogen Associated Molecular Patterns (PAMPs)

Damage Associated Molecular Patters (DAMPs)

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21
Q

What are PAMPs?

A

Shared molecular structures on microbial surfaces (eg. LPS)

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22
Q

What do DAMPs?

A

Damage to self-cells

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23
Q

How many receptors are there for PAMPs/DAMPs?

A

> 100

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24
Q

What do PRRs recognize?

A

PAMPs and DAMPs

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25
Q

How many receptors can engage with bacterium at same time?

A

Many

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26
Q

What do NK cells recognize?

A

Virally infected cells by recognizing changes at surface of human cells

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27
Q

What do resident macrophages have to recognize invading pathogens?

A

Phagocytic receptors which bind invaders and trigger phagocytosis

Signalling receptors that bind to pathogen and then instruct macophages to recruit additional cells to infected site

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28
Q

What type of receptors are phagocytic and signalling receptors on macrophages?

A

PRRs

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29
Q

What is the ligand for mannose receptor?

A

LPS, CPs

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30
Q

How are microorganisms phagocytosed by phagocytes?

A

Phagocytes contain receptors on surface that recognize components of microbe surface

Microorganisms are bound by phagocytic receptors on macrophage surface

Microorganisms are internalized by receptor-mediated endocytosis

Fusion of endosome with a lysosome forms a phagolysosome in which microorganisms are degraded

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31
Q

What are Toll-like receptors?

A

A family of 10 phagocyte signalling PRR receptors with variable specificity for a range of pathogens

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32
Q

How are Toll-like Receptors named?

A

TLR1 - TLR10

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33
Q

What shape and structure do TLRs have?

A

Horseshoe shape on outside surface (rich in leucine rich repeats (LRR) and a Toll-interleukin receptor (TIR) on the cytoplasmic side.

TLRs work in pairs as homodimers (2 of same type) or heterodimers (2 different TLRs come together)

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34
Q

What amino acid are TLRs rich in?

A

Leucine

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35
Q

What does the TIR domain do?

A

It activates response of TLRs

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36
Q

What is another name for TLRs?

A

CD281 - CD290

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37
Q

Are all TLRs facing the extracellular space?

A

No, some can face inside of endosomes.

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38
Q

What is the purpose of intracellular TLRs?

A

To recognize intracellular pathogens

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39
Q

Which TLRs form homodimers?

A

TLR3

TLR4

TLR5

TLR7

TLR8

TLR9

TLR10 (can also form heterodimer with TLR1 and 2)

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40
Q

Which TLRs form heterodimers?

A

TLR1:TLR2

TLR1:TLR10

TLR2:TLR6

TLR2:TLR10

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41
Q

What does TLR4 recognize?

A

LPS

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42
Q

Which pathogens typically have LPS?

A

Gram-negative bacteria (Remember outer membrane)

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43
Q

Which immune cells express TLR4?

A

Macrophages

Dendridic cells

Mast cells

Eosinophils

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44
Q

What does TLR3 recognize?

A

Double stranded viral RNA

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45
Q

Which cells express TLR3?

A

NK cells

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46
Q

Where are TLR3 receptors located? Why?

A

On endosomes, they recognize double stranded viral DNA and are signalling receptors.

This is a great way to recognize viruses and alert the immune system about the presence of viruses.

47
Q

What does TLR4 work with to recognise LPS?

A

It forms a complex with TLR4, MD2, and CD14 at cell surface.

48
Q

How does the TLR4, MD2, and CD14 complex bind LPS?

A

Complex is assembled binding LPS on macrophage surface.

TIR is expressed and it creates a signalling cascade which leads to NFkappaB activation which is a transcription factor that instigates cytokine release.

(TIR - MyD88 –> IRAK4 –> TRAF6 –> kinase cascade –> IKK –> NFkappaB –> degradation of IkappaB resulting in transcription of cytokines)

49
Q

What are LBPs?

A

LPS Binding Protein mediated transport down to receptor complex (TLR4-MD2-CD14)

50
Q

What does IkappaB do?

A

It is always bound to NFkappaB until it is degraded by binding of LPS to TLR4-MD2-CD14 complex and the triggering of the kinase cascade

51
Q

What happens if there is a mutation in NFkappaB activation due to lack of IKKgamma?

A

Results in immunological and developmental defects. (X-linked ectodermal dysplasia and immunodeficiency)

Unusual physical features also develop such as conical or missing teeth

52
Q

What are cytokines?

A

Short-lived molecules that exert influence within short distance from where they were made.

Signalling proteins which bind to cytokine receptors and induce intracellular signalling that change behaviour of second cell

53
Q

What do inflammatory cytokines do?

A

Act to create state of inflammation

54
Q

What do chemokines do?

A

Attract immune cells away from blood towards infected area

55
Q

What are the 5 most important cytokines that a macrophage makes?

A

IL-1beta

TNF-alpha

IL-6

CXCL8

IL-12

56
Q

What do IL-1beta and TNF-alpha do?

A

Induce blood vessels to become more permeable (more effector molecules can enter the infected tissue)

57
Q

What does IL-6 do?

A

Induces fat and muscle cells to metabolise and make heat to raise body temperature and create heat and raise temperature in infected tissue

58
Q

What does CXCL8 do?

A

Recruits neutrophils from blood into infected tissue

59
Q

What does IL-12 do?

A

Recruits and activates NK cells that in turn secretes cytokines that make macrophages’ response even stronger to infection

60
Q

What do IL-1beta, TNF-alpha, IL-6, CXCL8, and IL-12 collectively do?

A

They create a state of inflammation at site of infection

61
Q

What type of molecule is CXCL8?

A

It is a conformation of chemokine

62
Q

What are NOD-like receptors (NLRs)?

A

Receptors that detect products derived from intracellular degradation of phagocytosed pathogens

63
Q

What is the structure of NLRs like?

A

Receptors that detect products derived from intracellular degradation of phagocytosed pathogens

64
Q

What does NOD1 do?

A

Recognizes gamma-glutamyl diaminopimelic acid of gram-negatives

65
Q

What does NOD2 do?

A

Recognizes muramyl dipeptide of most bacteria

66
Q

How do NLRs recognize pathogen domains?

A

Leucine Rich Regions (LRRs)

Central nucleotide-binding oligomerisation domain (NOD)

Caspase-recruitment domain (CARD) at amino-terminal side

67
Q

What do NLRs do after binding to bacterial antigens?

A

They dimerise, bind kinase RIPK2

NLR bound -> NLRs dimerise -> bind kinase RIPK2 -> RIPK2 phosphorylates kinase TAK1 -> cascade of reactions leading to activation of NFkappaB -> transcription of cytokines

68
Q

What is the inflammasome?

A

It is formed by oligomerisation of NLRs.

69
Q

How do inflammasomes amplify innate immune response?

A

They produce IL-1beta

70
Q

What is important to know about IL-1beta?

A

It is hugely potent and can make you pretty sick so it must be tightly regulated.

71
Q

What ensures the right production of IL-1beta at the right time?

A

NLRs and the inflammasome

72
Q

How is the inflammasome produced?

A

NLRP3 comes together with adaptor protein and procaspase 1 (which cleaves pro-IL-1beta to activate it.

This can only happen once inflammasome is produced after oligomerisation of NLRs and procaspase 1 and adaptor protein.

73
Q

In what form is IL-1beta produced?

A

Inactive form which must be cleaved to function

74
Q

Which cells produce IL-1beta?

A

Activated cytokines

75
Q

What type of feedback mechanism do activated macrophages use to produce IL-1beta?

A

Positive feedback

76
Q

What domain is shared between TLRs and IL-1 receptor?

A

They both share the same TIR signalling domain

77
Q

What cytokines are activated by the inflammasome?

A

IL-1beta

IL-18

78
Q

What changes instigate oligomerisation of NLRs into inflammasome?

A

Ionic change in cytoplasm

79
Q

How do neutrophils enter the inflamed tissue and leave the bloodstream?

A

IL-8/CXCL8 bind to receptors on neutrophil causing it to bind to surface of blood vessel via complementary pairs of adhesion molecules; one which is on leukocyte surface and another on tissue cell surface.

80
Q

How do neutrophils move through blood when there is no infection?

A

Neutrophils travel rapidly through blood without interacting with vascular endothelium

81
Q

How do neutrophils roll around on blood vessel walls prior to extravasing at site of inflammation?

A

Cytokines induce expression of selectin on vascular endothelium which enables leukocyte binding.

Neutrophils express sialyl-LewisX

sialyl-LewisX (s-LeX) on leukocyte form transient interactions with selectin on endothelium causing neutrophils to “roll”

82
Q

What happens to blood vessels during inflammation and why?

A

Blood vessels dilate and blood flow decreases so neutrophils can interact with vessel walls, extravasate, and migrate to infection site.

83
Q

How do neutrophils extravasate?

A

Rolling adhesion

Integrins on leukocyte (LFA-1) and adhesion molecules on endothelium (ICAM-1) combine to halt rolling adhesion (A strong interaction is induced by CXCL8 held on proteoglycans of extracellular matrix and cell surface to form a gradient for leukocyte to travel)

Under guidance of chemokines, neutrophils squeeze between endothelial cells and penetrate connective tissue

Leukocyte migrates to center of infection along CXCL8 gradient.

84
Q

What type of protein is ICAM?

A

Immunoglobulin-like molecule

85
Q

What type of protein is LFA-1?

A

Integrin

86
Q

What is another name for extravasation?

A

Diapedesis

87
Q

What is the principal means by which immune system destroys invading pathogens?

A

Phagocytosis of microbes by phagocytic cells.

88
Q

What do macrophages do?

A

They are long lived, reside in tissues, work from very beginning of infection doing multiple functions

89
Q

What do neutrophils do?

A

Short-lived, dedicated killers, circulate in blood until they get stimulated by macrophages to enter tissue that is infected.

90
Q

How long are mature neutrophils kept in bone marrow for before being released into circulation?

A

5 days

91
Q

How many neutrophils enter tissues of mouth and throat daily?

A

3 billion

92
Q

What kind of conditions are neutrophils made to work in?

A

Anaerobic conditions and die after phagocytosis (within hours of entry to inflamed site)

93
Q

What is produced when there is a huge amount of neutrophil death?

A

Pus is formed

94
Q

How are neutrophils different to macrophages?

A

They have a wider range of phagocytic receptors and complement receptors.

They can engulf a greater range of particulate matter than macrophages and have greater diversity.

They have a greater diversity of microbicidal substances in granules.

95
Q

What kind of microbicidal substances are found in neutrophil granules?

A

Primary granules (contain myeloperoxidase)

Secondary granules (lactoferrin)

Tertiary granules (gelatinase)

96
Q

What do neutrophils do to kill bacteria after phagocytosis?

A

Granules full of lytic enzymes and substances as well as lysosome fuse with phagosome and thus bacteria is degraded.

Neutrophil then undergo apoptosis and are phagocytosed by a macrophage.

Dying neutrophils also produce extracellular traps (NETs)

97
Q

What do dying neutrophils produce?

A

Neutrophil extracellular traps (NETs)

98
Q

What is a NET?

A

A mesh matrix which can stick other creatures in this site holding them in place.

99
Q

What can macrophages do to the liver?

A

They produce IL-1/IL-6/TNF-alpha which act on the liver to produce acute-phase proteins which activate complement opsonisation

100
Q

What can macrophages do to the bone marrow endothelium?

A

Produce IL-1/IL-6/TNF-alpha which produce more neutrophils and increase phagocytosis

101
Q

What can macrophages do to the hypothalamous and muscle/fat?

A

They produce IL-1/IL-6/TNF-alpha which:

Increase body temperature

Protein and energy mobilization to generate increased body temperature

Resulting in a decreased viral and bacterial replication rate

102
Q

What are cytokines and other molecules that induce a fever called?

A

Pyrogens

103
Q

Where are pyrogens produced?

A

Exogenous (bacteria can produce them)

Endogenous (body can produce them)

104
Q

What does the hypothalamus do in response to pyrogens?

A

they release prostaglandins which raises hypothalamic thermostat to a higher temperature

105
Q

What are acute-phase protein functions?

A

Innate response occuring soon after start of infection

106
Q

Which acute phase proteins are involved in pathogen recognition?

A

C-reactive protein

Mannose-binding lectin

LPS-binding protein

107
Q

Which acute phase proteins are involved in pathogen elimination?

A

Complement components

108
Q

Which acute phase proteins are involved in the inflammatory response?

A

Granulocyte colony stimulating factor, serum amyloid A, secreted phospholipase A2

109
Q

What are acute phase proteins?

A

Diverse plasma proteins made rapidly in large amounts

110
Q

What happens to C-reactive protein levels and serum amyloid A after inflammatory stimulus?

A

They jump up in concentration immediately

111
Q

What happens to fibrinogen following inflammation?

A

Fibrinogen comes in slightly later (after several days)

112
Q

Which proteins are elevated post-inflammation/

A

C-reactive protein and serum amyloid increase immediately to huge levels.

C3 and fibrinogen are moderately elevated

Serum albumin drops during acute phase

113
Q

What does C-reactive protein look like?

A

It is a pentraxin (5 subunit family).

Polypeptide backbones of 5 subunits are traced by ribbons of different colour.

CRP resembles a pentagonal slab with hole in the middle.

IMED2001 (44 decks)

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