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Infection > Innate Immune System > Flashcards

Innate Immune System Flashcards

1
Q

What is the difference between infectivity and virulence?

A

Infectivity is ability to establish inside host

Virulence is ability to damage host

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2
Q

Define immune system?

A

Cells and organs that contribute to immune defences against infection and non-infections (i.e cancer/foreign objects). Differentiates between self-non-self

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3
Q

What is an infectious disease?

A

When a pathogen succeeds in overwhelming a host defence response to evade

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4
Q

What are 4 broad roles of the immune system?

A

Pathogen recognition
Containing infection
Minimising host damage
Memory for pathogens

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5
Q

4 characteristics of innate immunity?

A

Fast
Lack of specificity
Lack of memory
No change in intensity

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6
Q

4 characteristics of adaptive immunity?

A

Fast
Specific
Memory
Changes in intensity (same microbe 2nd time round much bigger immune response)

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7
Q

What are the roles of first lines of defence of innate immunity (2)?

A

Limit entry

Prevent growth

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8
Q

What are the 4 types of first line defence of innate immunity?

A

Physical
Chemical
Biological
Physiological

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9
Q

What are the three physical barriers?

A

Skin
Mucous membranes
Cilia

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10
Q

How do cilia help prevent infection?

A

Goblet cells secrete mucus catch pathogen cilia beat and mucus is coughed up. Upper resp tract has normal flora but lower resp tract should be sterile

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11
Q

What are the 4 physiological barriers?

A

Coughing
Sneezing
Vomit
Diarrhoea

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12
Q

What are 2 types of chemical barrier and name examples for each

A

pH
Skin 5.5
Vagina 4.4
Stomach 2-3

Antimicrobial molecules
Gastric pepsin and acid
Lysozymes
IgA
Mucous
Beta - defensins
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13
Q

What do each of the antimicrobial molecules do?

A

Gastric pepsin and acid - kills most microbes
Lysozymes - breaks bacterial cell wall
IgA - in tears sweat etc prevents microbe binding
Mucous - trap to expel
Beta - defensins - antimicrobial peptides toxic for both gram + and -

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14
Q

What is the biological barrier made up of and where?

A

Normal flora:

Skin
Nose/Pharynx
Mouth/Upper respiratory tract
GI - intestine
GU - vagina
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15
Q

Are normal flora seen around internal organs? blood?

A

No No

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16
Q

Name some benefits of normal flora

A

Compete with pathogens for resources and attachment sites so reduces their ability to establish
Makes vitamins e.g. Vit K
Antimicrobial properties

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17
Q

Give some examples of normal flora of the skin (5)

A 
Step pneumonia
Staph aureus
Staph epidermis
Candida albicans 
Clostridium perfringens
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18
Q

What does opportunistic mean? How is Candida albicans opportunistic?

A

Means normally unharmful and at low numbers, if normal flora reduced e.g. with antibiotics may be given the chance to grow and cause pathology e.g. Thrush

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19
Q

Give some examples of normal flora of the nasal cavity (3)

A

Strep pnuemoniae
Neisseria meningitidis
Haemophillus species

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20
Q

What is first vs second line defence of innate immunity?

A

First - barriers to entry of pathogen

Second - cells that contain and clear infection

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21
Q

How can normal flora become pathogenic/pathology related to reduction in normal flora? Give examples

A

DISPLACEMENT of flora from normal location to another site - e.g. staph aureus or strep viridans
Reduced normal flora by antibiotics = pathogen can invade - e.g. cdiff
Increased flora to pathological level e.g. if host immunocompromised like AIDS - e.g. candida albicans

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22
Q

What is the most common cause of normal flora being displaced to another site?

A

Poor dental hygiene/dental work

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23
Q

Which patients would need antibiotic prophylaxis before dental work (4)?

A

HIV - immunocompromised
Asplenic/Hyposplenic
Damaged or prosthetic valves
Previous infective endocarditis

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24
Q

Give some examples of what causes a patient to be immunocompromised/deplete normal flora and therefore at risk of overgrowth of microbes e.g. candida albicans

A 
HIV
Diabetes
Malignancy
Chemo
Antibiotics
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25
Q

How can chemotherapy predispose to infection by normal flora in terms of first line defence barriers?

A

Can cause mucositis - inflammation of mucosal membranes makes it easier for bacteria to permeate

26
Q

How does taking antacids predispose to colonisation of normal flora?

A

Increases pH, low pH is an innate barrier so increases chance of bacteria being able to establish and replicate

27
Q

What does the 2nd line defence do? What is in included?

A

Contain and clear infection

Phagocytes –> neutrophils/macrophages

Inflammation

28
Q

Do phagocytes recognise pathogens?

A

Yes

29
Q

Name some roles of macrophages. Are they present in all organs?

A

APC
Phagocyte
Produce cytokines
Angiogenesis

Yes

30
Q

What is the most common leukocyte present in the blood?

A

Neutrophils 60%

31
Q

What is the major WBC component of pus?

A

Neutrophils - so especially phagocytose pyogenic bacteria e.g. staph aureus staph pyogenes

32
Q

What recruits neutrophils?

A

Chemokines at site of infection

33
Q

Name three encapsulated bacteria splenic patients are particularly susceptible to developing

A

Neisseria meningitidis
Strep pneumoniae
Haemophillus influenzae

34
Q

What is the broad role of cytokines

A

Cell signalling

Eg recruitment of cells in inflammation

35
Q

Give two ways a phagocyte can recognise a pathogen

A

PRRs/PAMPs

Opsonisation

36
Q

How do PAMPs PRRs work?

A

PRRs on phagocytes recognise PAMPs on microbes.
There a variety of PRRs that recognise different things so can recognise a wide range of microbes
This allow the pathogen to attach to phagocytose

37
Q

What is the most common type of PRR?

A

Toll like receptor

38
Q

Why do PRRs not target host cells?

A

Because they don’t have PAMPs

39
Q

What is the PRR for gram neg bacteria that targets lipopolysaccharide (PAMP)?

A

Toll like receptor 4 (TLR4)

40
Q

What is the PRR for gram pos bacteria that targets peptidoglycan (PAMP)?

A

Toll like receptor 2 (TLR2)

41
Q

What is the PRR for gram neg lipopolysaccharide?

A

TLR4

42
Q

What is the PRR for gram pos peptidoglycan?

A

TLR2

43
Q

What is the PRR for all mycobacteria

A

TLR2

44
Q

What is an opsonin?

A

A coating protein that binds to microbes and leads to enhanced attachment of phagocytes

45
Q

Give three classes of opsonins and name some

A

Complement proteins - c3b c4b

Antibodies - IgG IgM

Acute phase proteins - CRP MBL (mannose binding lectin)

46
Q

Why is opsonisation really important for encapsulated bacteria?

A

As they resist phagocytosis

47
Q

How does a phagocyte come into contact with a pathogen?

A

Chemotaxis

Sometimes can randomly bump

48
Q

After the phagocyte has recognised the pathogen then what?

A

Phagocytosis

49
Q

What are the 7 stages of phagocytosis

A

1) Chemotaxis- adherence to microbe
2) Ingestion of microbe
3) Phagosome
4) Lysophagosome
5) Digest material - enzymes
6) Residual body
7) Eliminate waste

50
Q

What are two intracellular phagocyte killing mechanisms?

A

Oxygen dependent - using ROS - e.g. hydrogen peroxide, hydroxyl radical
Oxygen independent - e.g. lysosomal enzymes

51
Q

What two things help phagocytes in 2nd line defence?

A

Complement system

Cytokines

52
Q

What are three roles of complement system?

A

1) Recruitment of phagocytes - chemotaxis
2) Opsonisation
3) Membrane attack - killing of bacteria

53
Q

Which complement proteins do each of the 3 roles of the complement system?

A

1) c3a c5a
2) c3b c4a
3) c5-c9

54
Q

What are the antimicrobial actions of the complement system?

A

Same as asking what the three roles are

Recruitment
Opsonisation
Membrane attack

55
Q

What are two pathways of complement from the lecture?

A

Alternative pathway - C3 - initiated by cell surface microbial constituents

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

56
Q

What are three roles of cytokines

A

Chemoattraction
Phagocyte activation
Inflammation

57
Q

What cytokines do macrophages release?

A

IL-1 IL-6 TNF-alpha

58
Q

What do these do (4)?

A

1) Stimulate liver to produce opsonins - CRP/MBL
2) Stimulate neutrophil mobilisation from bone marrow
3) Inflamm actions - vasodilation, vasc permeability, adhesion molecules (attraction of neutrophils)
4) Hypothalamus - increased body temperature

59
Q

Which disease has no respiratory burst? Which enzyme is missing?

A

Chronic granulomatous disease (no NADPH oxidase)

60
Q

Which disease has no phagolysosome formation?

A

Chediak-Higashi syndrome

61
Q

What 3 conditions can reduce neutrophil number and therefore reduct innate immunity?

A

Chemo
Leukaemia/lymphoma
Certain drugs - phenytoin

62
Q

Lack/dysfunction of what organ can lead to reduced phagocytosis?

A

Spleen

Splenic macrophages

Infection (14 decks)

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