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Semester 3 - Infection > Session 3 - The innate immune system > Flashcards

Session 3 - The innate immune system Flashcards

1
Q

What two factors are required to infect a patient

A
  • Pathogen

* Mechanism of infection

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2
Q

What three separate variable factors effect the likelihood of infection of a patient

A
  • Number of pathogenic organisms present
  • Host immune response of patient
  • Virulence of the mechanism of infection
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3
Q

Define immune system

A

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

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4
Q

Define infectious disease

A

• When a pathogen succeeds in evading and/or overwhelming the host’s immune defences

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5
Q

Name four roles of the immune system

A

• Pathogen recognition
• Containing/eliminating the infection
• Regulating itself
- Remembering pathogens

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6
Q

How are pathogens recognised by the immune system?

A

• Cell surface and soluble receptors

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7
Q

Why does the immune system need to regulate itself?

A

• Minimum damage to host (resolution)

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8
Q

What are the two separate parts of the immune system

A
  • Innate immunity

* Adaptive immunity

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9
Q

Give four features of the innate immune system

A
  • Fast
  • Recognise groups of pathogens
  • Lack of memory
  • No change in intensity
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10
Q

Give four features of the adaptive immune system

A
  • Slow (3-4 days)
  • Specific to one pathogen
  • Immunologic memory
  • Increases in intensity
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11
Q

What happens to adaptive immunity if innate immunity does not exist?

A

• Becomes ineffective and useless

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12
Q

What four facets make up the first line of defence in the innate immune system

A
  • Physical barriers
  • Physiological barriers
  • Chemical barriers
  • Biological barriers
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13
Q

What is the overall purpose of the innate immune system

A

• To limit entry and growth of pathogens

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14
Q

Give three main mechanisms the innate immune system provides a physical barrier

A
  • Skin
  • Mucous membrane
  • Bronchial cillia
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15
Q

Name four places which mucous membranes which act as a physical barrier in the innate immune system

A
  • Mouth
  • Respiratory tract
  • GI tract
  • Urinary tract
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16
Q

Give four physiological barriers in the innate immune system

A
  • Diarrhoea
  • Vomiting
  • Coughing
  • Sneezing
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17
Q

Give two diseases in which diarrhoea is common

A
  • Food poisoning

* Allergies

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18
Q

Give three diseases in which vomiting is common

A
  • Food poisoning
  • Hepatitis
  • Meningitis
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19
Q

What are the two main categories of chemical barriers in the innate immune system

A
  • Low pH

* Antimicrobial molecules

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20
Q

Give three parts of the body with low pH

A
  • Skin (5.5) (glands)
  • Stomach (1-3) (gastric acid)
  • Vagina (4.4) (lactic acid species)
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21
Q

Name four antimicrobal molecules

A
  • IgA (tears, saliva)
  • Lysozyme
  • Mucous
  • Beta defensins
  • Gastric acid
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22
Q

What is the biological barrier?

A

• Normal flora of the body

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23
Q

Give 5 locations which have large colonies of normal flora

A
  • Nasopharynx
  • Mouth/throat
  • Skin
  • GI tract
  • Vagina
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24
Q

Outline three benefits of having a biological barrier

A
  • Compete with pathogens for attachment sites and resources
  • Produce antimicrobial chemicals
  • Synthesize vitamins (K, B12, other B vitamins)
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25
Q

Give three normal flora that inhabit the skin

A
  • Staphylococcus aureus
  • Staphylococcus epidermidis
  • Staphylococcus pyogenes
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26
Q

Give two normal flora that inhabit the nasopharynx

A
  • Neisseria meningitidis (1)

* Streptococcus pneumonia (2)

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27
Q

Give four ways in which normal flora is displaced from its normal location to a sterile location

A
  • Breaching the skin integrity
  • Fecal-oral route
  • Fecal-perineal-urethral route
  • Poor dental hygiene/dental work
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28
Q

How can the skin integrity be breached?

A
  • Skin loss
  • Surgery
  • Injection drug users
  • IV lines
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29
Q

Give three common causes of harmless bateraemia

A
  • Dental extraction
  • Gingivitis (inflammation of the gums)
  • Flossing
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30
Q

In what types of patients can displacement of normal flora cause serious infection?

A

`• Asplenic patients
• Patients with damaged or prosthetic valves
• Patients with previous infective endocaritis

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31
Q

What is the key treatment for patients at high risk of infection?

A

Antibiotic prophylaxis

32
Q

Give three things concerning flora that can cause clinical problems

A
  • When normal flora is displaced from its normal location
  • When normal flora overgrows and becomes pathogenic when host becomes immuno-compromised
  • When normal flora is depleted by antibiotcs
33
Q

In what four conditions can flora overgrow and become pathogenic

A
  • Diabetes
  • AIDs
  • Malignant diseases
  • Chemotherapy
34
Q

What can occur if normal flora is depleted by antibiotics (2 conditions)

A

• Intestine –> Severe colitis (C.difficile)

Vagina –> thrush

35
Q

What three factors make up the second line of defence?

A
  • Phagocytes
  • Chemicals

Inflammation

36
Q

What occurs in a phagocytic-microbe interaction

A
  • Recognition process

* Killing process of infectious microbes

37
Q

Name 7 key cells of the innate immune system

A
  • Macrophages
  • Monocytes
  • Neutrophils
  • Basophils
  • Eosinophils
  • Natural killer cells
  • Dendritic cells
38
Q

Where are macrophages found?

A

Present in all organs

39
Q

What is the function of macrophages?

A
  • Ingest and destroy microbes (Phagocytosis)
  • Present microbial antigens to T cells (adaptive immunity)
  • Produce cytokines/chemokines
40
Q

Where are monocytes found?

A

• Make up 5-7% of the blood

41
Q

What is the function of monocytes?

A

• Recruited at infection site and differentiate into macrophages

42
Q

Where are neutrophils found?

A
  • Present in blood

* Increased during infection

43
Q

What are neutrophils recruited by?

A

• Recruited by chemokines to the site of infection

44
Q

What do neutrophils do?

A

• Ingest and destroy pyogenic bacteria

○ Staph aureus and strep pyogenes

45
Q

What do basophils/mast cells do?

A

• Early actors of inflammation

Important in allergic responses

46
Q

What do eosinophils do?

A

• Defence against multi-cellular parasites

47
Q

What do natural killer cells do?

A

• Kill all abnormal host cells (virus infected or malignant)

48
Q

What do dendritic cells do?

A

• Present microbial antigens to T cells

49
Q

How do WBC recognise pathogens?

A

• Pathogen-associated molecular patterns
○ Carbohydrates, lipids, proteins, nucleic acids
• Pathogen recognition receptors
Toll like receptors

50
Q

What is opsonisation?

A

• Coating proteins called opsonins that bind to the microbial surface leading to enhanced attachment of phagocytes and clearance of microbes

51
Q

Give three categories of opsonins

A
  • Complement proteins
  • Antibodies
  • Acute phase proteins
52
Q

What are opsonins essential in clearing?

A

• Encapsulated bacteria
○ Neisseria meningitidis
○ Streptococcus pneumoniae
○ Heamophilus influenza

53
Q

Name an opsonising protein

A

• C3b

54
Q

Name an opsonising antibody

A

• IgG

55
Q

Give an opsonising acute phase protein

A

• C reactive protein

56
Q

What do phagocytes rely on to identify pathogens?

A
  • PAMPS

* Opsonins

57
Q

How do phagocytes destroy pathogens?

A
  • Engulfment

* Degradation of infectious microbes

58
Q

Outline process of phagocytosis

A
  • Chemotaxis and adherence of microbe to phagocyte
  • Ingestion of microbe by phagocyte
  • Formation of phagosome
  • Fusion of the phagosome with a lysosome to form a phagolysosome
  • Digestion of ingested microbe by enzymes
  • Formation of residual body containing indigestible material
  • Discharge of waste material
59
Q

Give two killing mechanisms of phagocytes

A
  • Oxygen dependent pathway

* Oxygen independent pathways

60
Q

Outline the oxygen dependent pathway of intracellular destruction

A

• Hydrogen peroxide produced which can destroy pathogens

61
Q

Outline an oxygen independent pathway

A
  • Lysozyme

* Lactoferrin or transferrin

62
Q

What is the complement system?

A
  • Perform various anti-microbial functions

* Made up of 20 serum proteins

63
Q

What are the two activating pathways?

A
  • Alternative pathway - initiated by cell surface microbial constituents
  • MBL pathway - Initiated when MBL binds to mannose containing residues of proteins found on salmonella
64
Q

Give three parts of the body involved in innate immunity

A
  • Liver (CRP and MBL)
  • Bone marrow (Neutrophil mobilisation)
  • Hypothalamus (high temperature)
65
Q

How does sepsis occur?

A
  • Microbial toxins cause
  • Overreaction of TLR4 receptor
  • Overreaction of complement
  • Excessive systemic inflammatory response
66
Q

Give four features of an excessive systemic inflammatory response

A
  • Cytokine shower
  • Coagulopathy
  • Vasodilation
  • Capillary Leak
67
Q

Give three ways in which phagocytosis can be reduced

A
  • Decrease spleen function
  • Decreased neutrophil number
  • Decreased neutropnhil function
68
Q

How can a patient undergo decreased spleen function?

A
  • Asplenic patients

* Hyposplenic patients

69
Q

How can a patient experience a decreased neutrophil number?

A
  • Cancer chemotherapy
  • Certain drugs
  • Leukaemia and lymphoma
70
Q

How can patient experience a decrease in neutrophil function?

A
  • Chronic granulomatous disease

* Chediak-Higashi syndrome (no phagolysosomes formed)

71
Q

What exactly does the spleen do?

A

• reservoir of WBC and platelets

Roughly 50% of WBC stored in the spleen

72
Q

What does removal of the spleen cause?

A
  • A state of immunodefiency

* Patient is vulnerable to sepsis

73
Q

Give three bacterium asplenic patient are vulnerable to

A

• Pneumococcus
• Haemophilus Ingluenzae
Meningococcus

74
Q

Describe streptococcus pneumoniae

A

Gram positive, encapsulated, lancet shaped bacterium

Acute bacterial pneumoniae

75
Q

What inhibits streptococcus pneumoniae?

A

Optochin

Semester 3 - Infection (14 decks)

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