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[ ESA 3- Infection and Immunity > Innate Immune System > Flashcards

Innate Immune System Flashcards

1
Q

What is the immune system?

A

Cells and organs that contribute to immune defences against infectious and non-infectious conditions

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2
Q

What is an infectious disease?

A

When the pathogen succeds in evading and/or overwhelming the host’s immune defences

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3
Q

What are the roles of the immune response?

A

Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens

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4
Q

What is required for the immune response to recognise pathogens?

A

Cell surface and soluble receptors

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5
Q

What is the purpose of pathogen recognition?

A

Distinguish between infectious and noninfectious diseases

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6
Q

How does the immune system contain/eliminate infection?

A

Killing and clearance mechanisms

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7
Q

Why is it important that the immune system regulates itself?

A

To produce minimum damage to the host, leading to resolution

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8
Q

Why does the immune system remember pathogens?

A

Prevents the disease for reoccurring

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9
Q

What are the features of the innate immune system?

A

Fast
Lack of specificity
Lack of memory
No change in intensity of response to primary or secondary encounters

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10
Q

How fast does the innate immune system act?

A

Within seconds

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11
Q

How specific is the innate immune system?

A

At best it can recognise groups of bacteria

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12
Q

What does the first line of immune defence consist of?

A

Barriers that limit entry and growth of pathogens at portals of entry

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13
Q

What are the barriers in the first line immune defence?

A

Physical barriers
Physiological barriers
Chemical barriers
Normal flora

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14
Q

What are the physical barriers in the innate immune system?

A

Skin
Mucous membranes
Bronchial cilia

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15
Q

What is the surface area of the skin?

A

1-2m squared

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16
Q

What do mucous membranes line?

A 
Cavities exposed to air; 
Mouth 
Respiratory tract
GI tract
Urinary tract
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17
Q

What is the purpose of bronchial cilia?

A

Waft trapped microbes to the pharynx for swallowing

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18
Q

What are the physiological barriers in the innate immune system?

A

Diarrhoea
Vomiting
Coughing
Sneezing

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19
Q

When is diarrhoea a physiological barrier?

A

In food poisioning

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20
Q

When is vomiting a physiological barrier?

A

Food poisioning
Hepatitis
Meningitis

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21
Q

When is coughing a physiological barrier?

A

Pneumonia

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22
Q

When is sneezing a physiological barrier?

A

Sinusitis

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23
Q

What are the chemical barriers to infection?

A

Low pH

Antimicrobial molecules

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24
Q

Where has low pH to resist infection?

A

Skin
Stomach
Vagina

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25
Q

What pH is the skin?

A

5.5

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26
Q

What pH is the stomach?

A

1-3

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27
Q

What pH is the vagina?

A

4.4

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28
Q

What causes the low pH of the vagina?

A

Lactobacillus commensal bacteria

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29
Q

What antimicrobials molecules consist the innate immune system?

A 
IgA
Lysozyme
Mucus
Beta-defensins
Gastric acid and pepsin
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30
Q

Where is IgA found?

A

Tears
Saliva
Mucous membranes

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31
Q

Where is lysozyme found?

A

Sebum
Respiration
Urine

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32
Q

Where is mucus found?

A

Mucous membrane

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33
Q

What secretes beta-defensins?

A

Mucous membrane epithelia

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34
Q

What is the normal flora?

A

Non pathogenic microbes that are found in strategic locations

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35
Q

Where are the normal flora found?

A 
Nasopharynx
Mouth/throat 
Skin
GI tract
Vagina
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36
Q

Where is normal flora absent?

A

Internal organs/tissues

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37
Q

What are the benefits of the normal flora?

A

Compete with pathogens for attachment sites and resources
Produce antimicrobial chemicals
Synthesise vitamins

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38
Q

What vitamins are synthesised by the normal flora?

A

K
B12
Other B vitamins

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39
Q

What organisms are found in the normal flora of the skin?

A 
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus pyogenes
Candida albicans
Clostridium perfringens
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40
Q

What organisms are found in the normal flora of the nasopharynx?

A

Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species

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41
Q

When can problems occur with the normal flora?

A

When normal flora is displaced from its normal location to a sterile location

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42
Q

How can normal flora be displaced from its normal location to a sterile location?

A

Breaching the skin integrity
Poor dental hygiene/dental work
Fecal-oral route
Fecal-perineal-urethral route

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43
Q

How can the skin integrity be breached?

A

Skin loss (burns)
Surgery
Injection drug uses
IV lines

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44
Q

What can poor dental hygiene and dental work lead to?

A

Bacteraemia

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45
Q

Give three examples of poor dental hygiene or dental work that can lead to bacteraemia

A

Dental extraction
Gingivitis
Brushing/flossing

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46
Q

What patients are at particular risk of dental related bacteraemia?

A

Asplenic/hyposplenic
Damaged or prosthetic heart valves
Previous infective endocarditis

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47
Q

When is the fecal-oral route likely?

A

In foodbourne infection

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48
Q

When is the fecal-perineal-urethral route likely?

A

Urinary tract infections in women

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49
Q

When may the normal flora become overgrown and pathogenic?

A

When the host becomes immunocompromised

When normal flora is depleted by antibiotics

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50
Q

What may cause a patient to be immunocompromised?

A

Diabetes
AIDS
Malignant disease
Chemotherapy

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51
Q

What can happen in the intestines when the normal flora is depleted by antibiotics?

A

Severe colitis resulting from clostridium difficile

52
Q

What can happen in the vagina when the normal flora is depleted by antibiotics?

A

Thrush resulting from candida albicans

53
Q

What is the second line of defence of the innate immune system?

A

Phagocytes and chemicals that cause inflammation to contain and clear the infection

54
Q

What cells are involved in innate immunity?

A 
Macrophages
Monocytes
Neutrophils
Basophils / mast cells 
Eosinophils
Natural Killer cells
Dendritic cells
55
Q

What kind of cells are macrophages, monocytes, and neutrophils?

A

Macrophages

56
Q

What organs are macrophages present in?

A

All organs

57
Q

What do macrophages do?

A

Ingest and destroy microbes in phagocytosis
Ingest microbial antigens to T cells in adaptive immunity
Produce cytokines/chemokines

58
Q

Where are monocytes present?

A

Blood

59
Q

What % of the blood are monocytes?

A

5-7%

60
Q

What do monocytes do?

A

Recruited to infection site and differentiated into macrophages

61
Q

Where are neutrophils present?

A

In the blood

62
Q

What % of blood leukocytes are neutrophils?

A

60%

63
Q

What happens to neutrophil numbers during infection?

A

Increased

64
Q

What recruits neutrophils to the site of infection?

A

Chemokines

65
Q

What do neutrophils do?

A

Ingest and destroy pyogenic bacteria

66
Q

Give two examples of pyogenic bacteria

A

S. aureus

Strep. pyogenes

67
Q

What is the role of basophils/mast cells?

A

Early actors of inflammation (vasomodulation)

68
Q

Where are basophils/mast cells important?

A

In allergic responses

69
Q

When are eosinophils important?

A

Defence against multi-cellular parasites (worms)

70
Q

What do NK cells do?

A

Kill all abnormal host cells (virus infected or malignant)

71
Q

What do dendritic cells do?

A

Present microbial antigens to T cells in acquired immunity

72
Q

How does pathogen recognition occur?

A

Through interactions between pathogen-associated molecular patterns (PAMPs) on the microbe and pathogen recognition receptors (PRRs) known as toll like receptors

73
Q

What are the PAMPS for gram negative bacteria?

A

Lipopolysaccharides (LPS)
Lipoproteins and lipopeptides
Porin

74
Q

What is the PRR for lipopolysaccharides?

A

TLR4

75
Q

What is the PRR for lipoproteins and lipopeptides?

A

TLR2

76
Q

What is the PRR for porins?

A

TLR2

77
Q

What are the PAMPs for gram +ve bacteria?

A

Peptidoglycan

Lipoteichoic acids

78
Q

What is the PRR for peptidoglycan?

A

TLR2

79
Q

What is the PRR for lipoteichonic acids?

A

TLR4

80
Q

What are the PAMPs for all mycobacteria?

A

Lipoarabinomannan

Mannose-rich glycans

81
Q

What is the PRR for lipoarabinomannan?

A

TLR2

82
Q

What is the PRR for mannose-rich glycans?

A

TLR2

83
Q

What is the PAMP for bacterial flagella?

A

Flagellin

84
Q

What is the PRR for flagellin?

A

TLR5

85
Q

What are opsonins?

A

Coating proteins

86
Q

What do opsonins do?

A

Bind to microbial surfaces

87
Q

What does the binding of opsonins lead to?

A

Enhanced attachment of phagocytes and clearance of phagocytes

88
Q

What are the classes of opsonins?

A

Complement proteins
Antibodies
Acute phase proteins

89
Q

Give 2 complement proteins that can act as opsonins

A

C3b

C4b

90
Q

Give two antibodies that can act as opsonins

A

IgG

IgM

91
Q

Give two acute phase proteins that can act as opsonins

A

C-reactive protein (CRP)

Mannose-binding lectin (MBL)

92
Q

What is opsonisation essential for?

A

Clearing encapsulated bacteria

93
Q

Give an example of an encapsulated bacteria

A

Neisseria meningitidis

94
Q

What do opsonins and PRRs work together to do?

A

Initiate phagocytosis

95
Q

What happens once a microbe has been recognised by receptors on the surface of the phagocyte?

A

The microbe is engulfed and destroyed

96
Q

What happens in the process of phagocytosis?

A
  1. Chemotaxis and adherence of microbe to phagocyte
  2. Ingestion of microbe by phagocyte
  3. Formation of a phagosome
  4. Fusion of the phagosome with a lysosome to form a phagolysosome
  5. Digestion of ingested microbe by enzymes
  6. Formation of a residual body containing indigestible material
  7. Discharge of waste material
97
Q

How do phagocytes kill pathogens?

A

Using different intracellular killing mechanisms

98
Q

What intracellular killing mechanisms are used by phagocytes?

A

Oxygen-dependant pathway (respiratory burst)

Oxygen independent pathways

99
Q

What happens in the oxygen-dependant pathway of phagocytic killing?

A

Releases toxic O2 products to kill the pathogens

100
Q

What toxic O2 products are released in the respiratory burst?

A 
Hydrogen peroxide
Hydroxyl radical 
Nitric oxide
Singlet oxygen
Hypophalite
101
Q

What are the oxygen-independent pathways of phagocytic killing?

A

Lysozyme
Lactoferrin or transferrin
Cationic proteins
Proteolytic and hydrolytic enzymes

102
Q

Give an example of a cationic protein

A

Cathepsin

103
Q

What does the complement system consist of?

A

20 serum proteins

104
Q

What are the most important serum proteins in the complement system?

A

C1-9

105
Q

What does C3a and C5a do?

A

Recruit phagocytes

106
Q

What does C3b-C4b do?

A

Opsonise pathogens

107
Q

What does C5-C9 do?

A

Kill pathogens by membrane attack complex

108
Q

What are the activating pathways of the complement system?

A

Alternative pathway

MBL pathway

109
Q

What happens in the alternative pathway of complement activation?

A

Complement initiated by cell surface microbial constituents

110
Q

What happens in the MBL pathway of complement activation?

A

Complement initiated when MBL binds to mannose containing residues of proteins found on many microbes

111
Q

Give a microbe that will induce the alternative pathway of complement activation

A

Endotoxins on E. Coli

112
Q

Give two microbes that will induce the MBL pathway of complement activation

A

Salmonella spp.

Candida albicans

113
Q

What to cytokine/chemokines cause?

A

Chemoattraction
Phagocyte activation
Inflammation

114
Q

Give three chemokines

A

TNF-alpha
IL-1
IL-6

115
Q

Where do TNF-alpha, IL-1, and IL-6 have effects?

A

Liver
Bone marrow
Hypothalamus
Also have inflammatory actions

116
Q

What is the effect of chemokines in the liver?

A

Release CRP

Release MBL, leading to complement activation

117
Q

What is the effect of chemokines in the bone marrow?

A

Neutrophil mobilisation

118
Q

What is the inflammatory effect of chemokines?

A

Vasodilation
Vascular permeability
Adhesion molecules lead to attraction of neutrophils

119
Q

What is the effect of chemokines in the hypothalamus?

A

Increased body temperature

120
Q

When do clinical problems start with the innate immune system?

A

When there is decreased phagocytosis

121
Q

When may someone have decreased phagocytosis?

A

Decrease in spleen function
Decreased neutrophil number
Decreased neutrophil function

122
Q

When may someone have decreased spleen function?

A

Asplenic/hyposplenic patients

123
Q

When may someone have decreased neutrophil numbers?

A

Cancer chemotherapy
Certain drugs
Leukaemia and lymphoma

124
Q

Give a drug that could lead to decreased neutrophil numbers

A

Phenytoin

125
Q

When may someone have decreased neutrophil function?

A

Chronic granulomatous disease

Chediak-Higashi syndrome

126
Q

Why does chronic granulomatous disease cause a decrease in neutrophil function?

A

No respiratory burst

127
Q

Why does Chediak-Higashi syndrome lead to reduced neutrophil function?

A

No phagolysosome formation

[ ESA 3- Infection and Immunity (15 decks)

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