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Infection A > Session 3 Lecture 2 > Flashcards

Session 3 Lecture 2 Flashcards

1
Q

Define virulence ?

A

The capacity of the microbe to damage the host

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2
Q

Define immune system

A

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

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3
Q

Define an infectious disease

A

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

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4
Q

What is the largest lymphoid organ in the body?

A

Spleen

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5
Q

What are the four main features of the immune response?

A

Pattern recognition, Containing/eliminating the infection, Regulating itself and remembering pathogens

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6
Q

What is meant by pattern recognition in the immune response?

A

Cell surface and soluble receptors determine whether something is self or non self

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7
Q

What is meant by ‘regulating itself’ in the immune response?

A

Minimum damage to the host (resolution)

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8
Q

What are the two different types of immune response?

A

Innate immunity and adaptive immunity

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9
Q

Describe the features of innate immunity

A

Immediate protection - Fast, Lack of specificity, Lack of memory and No change in intensity

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10
Q

Describe the features of adaptive immunity

A

Long lasting - Slow, Specificity, Immnunologic memory and Changes in intensity

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11
Q

What would happen if you don’t have an innate immune response?

A

You would not get an adaptive immune response either because the innate activates the adaptive.

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12
Q

What are the first line of defence in the body?

A

Physical barriers, physiological barriers, chemical barriers and biological barriers.

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13
Q

What is the aim of the first lines of defence?

A

They prevent entry and limit growth of pathogens

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14
Q

Give some examples of physical barriers

A

Skin, mucous membrane and bronchiole cilia

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15
Q

Give some example of physiological barriers

A

Diarrhoea, vomiting, coughing and sneezing

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16
Q

Give some examples of chemical barriers

A

Low pH and antimicrobial molecules

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17
Q

Give some examples of biological barriers

A

Normal flora

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18
Q

Give examples of normal flora that inhabit the skin

A

Staphylococcus aureus, streptococcus pyogenes

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19
Q

Give examples of normal flora that inhabit the nasopharyx

A

Streptococcus pneumoniae, neisseria meningitidis

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20
Q

With regards to normal flora, when to clinical problems start?

A

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

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21
Q

How can normal flow be displaced from its normal location?

A

Breaching skin integrity, faecal oral route, faecal-perineal-urethral route (UTI) and poor dental hygiene.

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22
Q

What are considered to be high risk patients? (With regards to a serious infection caused by normal flora)

A

Patients who

  • Asplenic/hyposplenic
  • Damaged or prosthetic valves
  • Previous infective endocarditis
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23
Q

What are the second lines of defence?

A

Phagocytes, chemicals and inflammation

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24
Q

What is the aim of the second lines of defence?

A

They will contain and clear the infection

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25
Q

What are the main phagocytes?

A

Macrophages, monocytes and neutrophils

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26
Q

What is the function of macrophages?

A
  • Phagocytosis
  • Present microbial agents to T cells
  • produce cytokines/chemokines
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27
Q

Where are macrophages found?

A

Present in all organs

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28
Q

Where are monocytes found?

A

Present in the blood (5-7%)

29
Q

What is the function of monocytes?

A

Recruited at infection site and differentiate into macrophages

30
Q

Where are neutrophils found?

A

Present in the blood (69% of blood leukocytes) Increase during infection

31
Q

What is the function of neutrophils?

A
  • Recruited by chemokines to the site of infection

- Ingest and destroy progenitor bacteria; staph aureus and strep pyogenes

32
Q

What other key cells are involved in innate immunity?

A

Basophils/mast cells, eosinophils, natural killer cells and dendritic cells

33
Q

What is the function of basophils/mast cells?

A
  • Early actors of inflammation (vasodilation)

- Important in allergic responses

34
Q

What is the function of eosinophils?

A

Defence against multi-cellular parasites (worms)

35
Q

What is the function of natural killer cells?

A

Kill all abnormal host cells (virus infected or malignant)

36
Q

What is the function of dendritic cells?

A

Present microbial antigens to T cells (acquired immunity)

37
Q

Once a phagocyte and microbe interact, what happens next?

A
  • Recognition process

- Killing process of infectious microbe

38
Q

What are PAMPs?

A

Pathogen associated molecular pattern. They are molecules associated with groups of pathogens that are recognised by cells of the innate immune system.

39
Q

What are PRRs?

A

Pathogen Recognition Receptors. These are proteins expressed by cells of the innate immune system to identify two classes of molecules - PAMPs and DAMPs.

40
Q

What is the difference between PAMPs and DAMPs?

A

PAMPs are associated with microbial pathogens and DAMPs are associated with cell components that are released during cell damage/death.

41
Q

Why we do need receptors inside cells as well?

A

Because viruses replicate inside the cell and we need to be able to detect this.

42
Q

What is opsonisation of microbes?

A

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

43
Q

Give some examples of opsonins

A

Complement proteins - C3b, antibodies IgG, acute phase protein CRP

44
Q

What is a phagolysosome?

A

This is when a lysosome has bruised with a phagocytic vesicle.

45
Q

What are the two different phagocyte intracellular killing mechanisms?

A
  • Oxygen dependent pathway

- Oxygen independent pathway

46
Q

What is the oxygen-dependent pathway?

A

When phagocyte ingests bacteria, its oxygen consumption increases. This increases produces reaction O2 containing molecules that are anti-microbial. Eg hydrogen peroxide and nitric oxide

47
Q

What is respiratory burst?

A

This is the rapid release of reactive oxygen species from different cell types.

48
Q

What is the oxygen independent pathway?

A

This is when phagocytes kill microbes by oxygen independent ways. There are four different types.

49
Q

What are the different methods of killing a cell via the oxygen independent pathway?

A

Use: lysosome; lactoferrin; cationic proteins or proteolytic hydrolytic enzymes

50
Q

How does lactoferrin kill a microbe?

A

Removes the essential iron from bacteria

51
Q

How do cationic proteins kill a microbe?

A

These are electrically charged proteins that damage the bacteria membrane

52
Q

What does the complement system consist of?

A

Complement pathways

20 serum proteins (most important C1-C9)

53
Q

What are the different pathways of the complement system?

A
  • Alternative pathway

- MBL pathway

54
Q

How is the alternative pathway initiated?

A

Cell surface microbial constituents

55
Q

How is the MBL pathway initiated?

A

MBL binds to mannose containing residues on proteins found on many microbes

56
Q

What does MBL stand for?

A

Mannose binding lectin

57
Q

What are the functions of C3a and C5a?

A

Recruitment of phagocytes

58
Q

What are the functions of C3b - C4b ?

A

Opsonisation of pathogens

59
Q

What are the functions of C5 - C9 ?

A

Killing of pathogens membrane attack complex

60
Q

What do cytokines/chemokines cause?

A

Chemoattraction, phagocyte activation and inflammation

61
Q

What antimicrobial actions does the bone marrow do?

A

Neutrophil mobilisation

62
Q

What antimicrobial actions does the hypothalamus do?

A

Increased body temperature

63
Q

What anti-microbial effects does the inflammatory response have?

A
  • Vasodilation
  • Vascular permeability
  • Adhesion molecules therefore attraction of neutrophils
64
Q

What anti-microbial effects does the liver have?

A
  • CRP

- MBL - complement activation

65
Q

With regards to infection, when do clinical problems start?

A

When phagocytosis is reduced

66
Q

Why might you have reduced phagocytosis?

A
  • Decreased spleen function
  • Decreased neutrophil number
  • Decreased neutrophil function
67
Q

Why might you have decreased neutrophil number?

A

Cancer chemotherapy, certain drugs or leukaemia/lymphoma

68
Q

Why might you have decreased neutrophil function?

A
  • Chronic granuloma disease (no respiratory burst)

- Chediak-Higashi syndrome (no phagolysosome formation)

Infection A (18 decks)

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