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Infection And Immunity > Host Defence Mechanisms > Flashcards

Host Defence Mechanisms Flashcards

1
Q

what are the 4 genres of host defence mechanisms?

A
  1. normal flora
  2. mechanical processes
  3. Immune system
  4. physical barriers
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2
Q

name 5 physical barriers

A
  1. tears- lysozyme
  2. Skin- dry, acidic, sweat containing fatty and lactic acid.
  3. filtration of inhaled air by turbinate bones.
  4. commensal bacteria in GI and skin
  5. acidity of stomach and vagina
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3
Q

what is the hosts mechanical defences?

A

Mucociliary action and Flushing

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4
Q

whats Mucociliary action?

A

mucous prevents attachment and is pushed to the throat by ciliated epithelia.

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5
Q

define flushing

A

flow of fluid over mucosal surface removing bacteria.

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6
Q

give some exiles of flushing?

A
  1. urine flow over urogenital tract
  2. gut contents in GI tract
  3. tears over cornea
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7
Q

how is the normal human flora a defence mechanism?

A
  1. exclude colonisation by competition
  2. induce low level antibody and react with the pathogen
  3. produce antimicrobials bacteriocin and fatty acids.
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8
Q

explain 4 ways the hosts immune system acts as a defence?

A
  1. inhibitory compounds
  2. specialised immune cells
  3. secretory immunity
  4. systemic immunity via Ab
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9
Q

name 5 inhibitory compounds

A
  1. HCL - stomach
  2. Bile salts and fatty acids.
  3. Defensins
  4. Lactoferrin and transferrin
  5. Lysozyme.
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10
Q

whats the action of lysozyme?

A

cleaves peptidoglycan and disrupts the cell wall found in saliva and tears

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11
Q

whats the action of Lactoferrin?

A

found in body secretions and serum binds to free iron so inaccessible to bacteria.

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12
Q

whats the action of Defensins?

A

pore forming cationic peptides

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13
Q

name the specialised immune cells that are involved in the hosts defence

A

phagocytic cells, Kupffer cells mesagnial cells and alveolar macrophages

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14
Q

name the cells of the reticuloendothelial system

A

lung- alveolar macrophages
kidney- mesagnial cells
liver- Kupffer cells
peridontal tissue- gingival macrophage.

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15
Q

describe secretary immunity

A
  1. sIgA inhibits bacterial attachment to mucosal epithelium.
  2. agglutinates bacteria
  3. binds inactive toxins
  4. presents in colostrum so protects suckling infants.
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16
Q

define virulence

A

the potential for a pathogen to produce morbidity or mortality in infected hosts

17
Q

define virulence factors

A

properties that enable a microorganism to establish itself on/within a host of a particular species + enhance its potential to cause disease.

18
Q

name the 8 bacterial virulence factors

A
  1. capsule
  2. fimbriae
  3. type III secretion system
  4. siderophores
  5. endotoxin
  6. toxins
  7. biofilms
  8. serum resistance
19
Q

how does the capsule protect the host?

A

surface polysaccharides protect against host immune defence

20
Q

how does serum resistance protect the cell?

A

surface molecules mediate resistance to complement

21
Q

how do biofilms protect bacteria?

A

attachment and persistence

22
Q

how do toxins protect the cell?

A

secreted (exo) or membrane bound (endo) proteins cause tissue damage or inhibit tissue function.

23
Q

how do siderophores protect bacteria?

A

scavenge iron and promote uptake into bacteria

24
Q

name an endotoxin and how it works

A

lipopolysaccharides are components of membranes elicit immune/inflammatory response.

25
Q

how is fimbriae a virulence factor?

A

adheres to host tissues and is subject to Ag variation.

26
Q

how do type III secretion systems work?

A

adherence to and invasion of host tissues

27
Q

what are the 6 stages if bacterial infection?

A
  1. entry
  2. colonisation
  3. proliferation
  4. invasion
  5. immune evasion
  6. transmission
28
Q

how does entry occur?

A
  1. skin is major barrier breached by bites and wounds

2. entry via mucosal surfaces

29
Q

what is colonisation?

A

attachment to mucosal surfaces

30
Q

what is proliferation?

A

acquisition of nutrients and overcoming Fe limitation

31
Q

what is invasion?

A

entry into host tissue/cell local/systemic

32
Q

what is immune evasion?

A

avoidance of the immune system via Ag/phase variation and resistance to immune effects.

33
Q

whats the prevalence of UTI?

A

10-20% woman 12% men

34
Q

what causes UTI?

A

90% E. coli

35
Q

how do you treat UTI?

A

oral ampicillin or IV gentamicin

36
Q

how does UTI infection occur?

A

contamination by bacteria from the GI tract

37
Q

describe the virulence factors present in Neisseria meningitides

A
  1. capsule
  2. LPS
  3. pilus
    4 Tbp, Lbp, Hpu, HmnR, FetA
  4. Opa, Opc, NhhA, NadA.

Infection And Immunity (16 decks)

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