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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
Give three normal flora that inhabit the skin
* Staphylococcus aureus * Staphylococcus epidermidis * Staphylococcus pyogenes
26
Give two normal flora that inhabit the nasopharynx
* Neisseria meningitidis (1) | * Streptococcus pneumonia (2)
27
Give four ways in which normal flora is displaced from its normal location to a sterile location
* Breaching the skin integrity * Fecal-oral route * Fecal-perineal-urethral route * Poor dental hygiene/dental work
28
How can the skin integrity be breached?
* Skin loss * Surgery * Injection drug users * IV lines
29
Give three common causes of harmless bateraemia
* Dental extraction * Gingivitis (inflammation of the gums) * Flossing
30
In what types of patients can displacement of normal flora cause serious infection?
`• Asplenic patients • Patients with damaged or prosthetic valves • Patients with previous infective endocaritis
31
What is the key treatment for patients at high risk of infection?
Antibiotic prophylaxis
32
Give three things concerning flora that can cause clinical problems
* 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
In what four conditions can flora overgrow and become pathogenic
* Diabetes * AIDs * Malignant diseases * Chemotherapy
34
What can occur if normal flora is depleted by antibiotics (2 conditions)
• Intestine --> Severe colitis (C.difficile) | Vagina --> thrush
35
What three factors make up the second line of defence?
* Phagocytes * Chemicals Inflammation
36
What occurs in a phagocytic-microbe interaction
* Recognition process | * Killing process of infectious microbes
37
Name 7 key cells of the innate immune system
* Macrophages * Monocytes * Neutrophils * Basophils * Eosinophils * Natural killer cells * Dendritic cells
38
Where are macrophages found?
Present in all organs
39
What is the function of macrophages?
* Ingest and destroy microbes (Phagocytosis) * Present microbial antigens to T cells (adaptive immunity) * Produce cytokines/chemokines
40
Where are monocytes found?
• Make up 5-7% of the blood
41
What is the function of monocytes?
• Recruited at infection site and differentiate into macrophages
42
Where are neutrophils found?
* Present in blood | * Increased during infection
43
What are neutrophils recruited by?
• Recruited by chemokines to the site of infection
44
What do neutrophils do?
• Ingest and destroy pyogenic bacteria | ○ Staph aureus and strep pyogenes
45
What do basophils/mast cells do?
• Early actors of inflammation | Important in allergic responses
46
What do eosinophils do?
• Defence against multi-cellular parasites
47
What do natural killer cells do?
• Kill all abnormal host cells (virus infected or malignant)
48
What do dendritic cells do?
• Present microbial antigens to T cells
49
How do WBC recognise pathogens?
• Pathogen-associated molecular patterns ○ Carbohydrates, lipids, proteins, nucleic acids • Pathogen recognition receptors Toll like receptors
50
What is opsonisation?
• Coating proteins called opsonins that bind to the microbial surface leading to enhanced attachment of phagocytes and clearance of microbes
51
Give three categories of opsonins
* Complement proteins * Antibodies * Acute phase proteins
52
What are opsonins essential in clearing?
• Encapsulated bacteria ○ Neisseria meningitidis ○ Streptococcus pneumoniae ○ Heamophilus influenza
53
Name an opsonising protein
• C3b
54
Name an opsonising antibody
• IgG
55
Give an opsonising acute phase protein
• C reactive protein
56
What do phagocytes rely on to identify pathogens?
* PAMPS | * Opsonins
57
How do phagocytes destroy pathogens?
* Engulfment | * Degradation of infectious microbes
58
Outline process of phagocytosis
* 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
Give two killing mechanisms of phagocytes
* Oxygen dependent pathway | * Oxygen independent pathways
60
Outline the oxygen dependent pathway of intracellular destruction
• Hydrogen peroxide produced which can destroy pathogens
61
Outline an oxygen independent pathway
* Lysozyme | * Lactoferrin or transferrin
62
What is the complement system?
* Perform various anti-microbial functions | * Made up of 20 serum proteins
63
What are the two activating pathways?
* Alternative pathway - initiated by cell surface microbial constituents * MBL pathway - Initiated when MBL binds to mannose containing residues of proteins found on salmonella
64
Give three parts of the body involved in innate immunity
* Liver (CRP and MBL) * Bone marrow (Neutrophil mobilisation) * Hypothalamus (high temperature)
65
How does sepsis occur?
* Microbial toxins cause * Overreaction of TLR4 receptor * Overreaction of complement * Excessive systemic inflammatory response
66
Give four features of an excessive systemic inflammatory response
* Cytokine shower * Coagulopathy * Vasodilation * Capillary Leak
67
Give three ways in which phagocytosis can be reduced
* Decrease spleen function * Decreased neutrophil number * Decreased neutropnhil function
68
How can a patient undergo decreased spleen function?
* Asplenic patients | * Hyposplenic patients
69
How can a patient experience a decreased neutrophil number?
* Cancer chemotherapy * Certain drugs * Leukaemia and lymphoma
70
How can patient experience a decrease in neutrophil function?
* Chronic granulomatous disease | * Chediak-Higashi syndrome (no phagolysosomes formed)
71
What exactly does the spleen do?
• reservoir of WBC and platelets | Roughly 50% of WBC stored in the spleen
72
What does removal of the spleen cause?
* A state of immunodefiency | * Patient is vulnerable to sepsis
73
Give three bacterium asplenic patient are vulnerable to
• Pneumococcus • Haemophilus Ingluenzae Meningococcus
74
Describe streptococcus pneumoniae
Gram positive, encapsulated, lancet shaped bacterium | Acute bacterial pneumoniae
75
What inhibits streptococcus pneumoniae?
Optochin

Semester 3 - Infection (14 decks)

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