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Infection > 4. Innate Immunity > Flashcards

4. Innate Immunity Flashcards

1
Q

What is infectivity?

A

Ability of a microbe to establish itself within and on host

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2
Q

What is virulence?

A

Capacity of pathogen to do damage in host cell

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3
Q

What is the definition of the immune system?

A

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

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4
Q

What is the most important organ in the immune system?

A

Spleen

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5
Q

What is the definition of an infectious disease?

A

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

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6
Q

What are the roles of the immune system?

A

Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens

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7
Q

What is innate immunity?

A

Natural immunity
Immediate protection
Fast, lack of specificity, lack of memory, no change in intensity

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8
Q

What is adaptive immunity?

A 
Long lasting 
Slow
Specificity
Immunological memory - gives stronger and faster immune response 
Changes in intensity
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9
Q

What are the first lines of defence in the innate immunity?

A

Physical barriers
Physiological barriers
Chemical barriers
Biological barriers

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10
Q

What are the physical innate barriers?

A

Skin
Mucous membranes
Bronchial cilia

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11
Q

What are the physiological innate barriers?

A

Diarrhoea
Vomiting
Coughing
Sneezing

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12
Q

What are the chemical innate barriers?

A

Low pH

Antimicrobial molecules

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13
Q

What microbial barriers are involved in the chemical barriers?

A 
IgA (tears, salvias mucous membrane) - prevents microbe attaching to host
Lysozyme (sebum, perspiration, urine)
Mucus - traps microbes
Beta-defensins (epithelium)
Gastric acid and pepsin
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14
Q

What are the biological barriers?

A

Normal flora: non pathogenic microbes, strategic locations (nasopharynx, mouth/throat, skin, GI tract, vagina)

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15
Q

What are the benefits of biological barriers?

A

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

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16
Q

What are some example of normal flora that inhabit the skin?

A

Staphylococcus aureus/epidermidis/pyogenes
Candida albicans
Clostridium perfringens

17
Q

What are examples of normal flora that inhabit the nasopharynx?

A

Streptococcus pneumoniae
Neisseria meningitis
Haemophilus species

18
Q

When do clinical problems start with normal flora?

A 
When normal flora is displaced from its normal location to sterile location 
Breaching the skin integrity
Faecal-oral route
Faecal-perineal-urethral route 
Poor dental hygiene/dental work
19
Q

Who are the high risk patients for serious infections?

A

Asplenic and hyposplenic patients
Patients with damaged or prosthetic valves
Patients with previous infective endocarditis

20
Q

What are macrophages?

A

Present in all organs
Ingest and destroy microbes (phagocytosis)
Present microbial antigens to T cells
Produce cytokines/chemokines

21
Q

What are monocytes?

A

Recruited a infection site and differentiate into macrophages

22
Q

What are neutrophils?

A

Increased during infection
Recruited by chemokines to site of infection
Ingest and destroy pyogenic bacteria

23
Q

What are basophils/mast cells?

A

Early actors of inflammation (vasomodulation)

Importance in allergic responses

24
Q

What are eosinophils?

A

Defence against multi-cellular parasites

25
Q

What are natural killer cells?

A

Kill all abnormal host cells

26
Q

What are dendritic cells?

A

Present microbial antigens to T cells

27
Q

What microbial structures are involved in pathogen recognition?

A

Pathogen-associated molecular pathogens (PAMPs)

- carbohydrates, lipids, proteins, nucleic acids

28
Q

What are PRRs?

A

Pathogen recognition receptors on phagocytes

29
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

30
Q

Give examples of opsonins

A

Complement proteins: C3b, C4b
Antibodies: IgG, IgM
Active phase proteins: C-reactive protein, MBL

31
Q

What does the opsonins receptor do?

A

Signals phagocyte to engulf microbe

32
Q

Describe 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 phagosome with a lysosome to form phagolysosome
    5 Digestion of ingested microbe by enzymes
  5. Formation of residual body containing indigestible material
  6. Discharge of waste materials
33
Q

What are the 2 phagocytes intracellular killing mechanisms?

A

Oxygen-dependent pathway (respiratory burst)
- toxic O2 products for pathogens
Oxygen-independen pathways
- lysozyme, proteolytic and hydrologic enzymes

34
Q

What are the 2 activation pathways in the complement system?

A

Alternative pathway

MBL pathway

35
Q

When is alternative pathway initiated?

A

Initiated by cell surface microbial constituents (endotoxins)

36
Q

When is MBL pathway initiated?

A

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

37
Q

What are the antimicrobial actions in the alternative pathway?

A

C3a and C5a: recruitment of phagocytes
C3b-C4b: opsonisation of pathogens
C5-C9: killing of pathogens, membrane attack complex

38
Q

What are cytokines and chemokines involved in?

A

Chemoattraction
Phagocyte activation
Inflammation

39
Q

What are the clinical problems when phagocytosis is reduced?

A

Decreased spleen function
Decreased neutrophil number
Decreased neutrophil function

Infection (18 decks)

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