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cellular basis of immunity > 6 - bacterial immunity > Flashcards

6 - bacterial immunity Flashcards

1
Q

features of innate protection

A

broad
low-level
fast
many different pathogens

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2
Q

features of adaptive immunity

A

slower
specific for a particular microorganism
high-level protection

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3
Q

innate recognition

A

recognises molecules that have common characteristics of bacteria but are foreign to the host

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4
Q

innate receptors are ..

A

pre-coded to recognise a limited repetoire of molecules

PAMPs

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5
Q

2 innate killing mechanisms

A

complement pathway

phagocytosis

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6
Q

how is alternitve pathway activated

A

recognisiton of cell surface proteins and polysaccharides eg LPS

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7
Q

how is classical complement pathway activated

A

triggered by antibodies (bound IgM or IgG) binding to antigens

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8
Q

how is lectin complement pathay activated

A

by carbohydrates like mannose and N-acetylglycosamine

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9
Q

early events of complement

A

different for each pathway but all generate a protease

e.g. C3 convertase

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10
Q

C3 component cleaves to form

A

C3a and C3b

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11
Q

C3b

A

bound to surface of bacteria

means response is localised (no collateral damage)

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12
Q

role of C5 convertase

A

cleaves C5 to C5a and C5b

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13
Q

which component of complement becomes MAC

A

C5b

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14
Q

which components of complement are the effectors

A

C3a and C5a

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15
Q

what is the main effect of C3a and C5a

A

promote inflammation

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16
Q

how to C3a and C5b promote inflmmation

A

bind to mast cells via their receptors
- cause degranulation and release of histamine
promote vasoldilation providing access to other immune cells

act as chemoattractants - signal to phagocytes

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17
Q

how does membrane attack complex (MAC) work

A

composed of some C9 subunits
forms a pore in target membrane
promotion of unregulated movement of ions across membrane
bacterial cell lysis

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18
Q

C1q deficiency

A

leads to sepsis and meningitis

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19
Q

C3 deficiency

A

leads to respiratory tract infections and meningitis

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20
Q

types of recognition for phagocytic killing

A

direct

indirect

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21
Q

direct recognition - phagocytes

A

via antibody receptors (Fc)

via C3b receptors

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22
Q

indirect recognition - phagocytes

A

PRRs

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23
Q

TLRs

A

type of PRR

embedded in membrane of phagocytic cell

24
Q

structure of TLR

A

horseshoe - extracellular

dimerisation occurs intracellularly

25
Q

describe TLR recognition –> signalling

A 
PAMP binds
dimerisation 
signalling cascade leads to activation of T factors e.g. NF-kappaB
cytokine production 
inflammatory response
26
Q

5 examples of cytokines

A 
IL-1
IL-6
TNF-a
Interferon-a
interferon-B
27
Q

role of IL-1

A

activates endothelial cells

causes fever

28
Q

IL-6 role

A

proliferation of antiobody-producing B cells

29
Q

effects of TNF-a

A

activates endothelial cells
causes fever
activates neutrophils

30
Q

effects of interferon-a and interferon-B

A

anti-viral immunity
promotes CD4+ and CD8+
T cell response

31
Q

interferon-a used to treat

A

Hep A/B viral

32
Q

interferon-B used to treat

A

multiple sclerosis

33
Q

effect of bacteria binding to TLR

A

triggers ingestion and uptake into the phagocyte

bacteria then enters the phagosome and fuses with the lysosome –> phagolysosome

34
Q

killing mechanisms of phagolysosome

A

lowers pH
enzymes (lysozymes, proteases)
oxygen-free radicals

35
Q

oxygen free radicals

A

e.g. hydrogen peroxide
superoxide

generated by phagocytic cell and put into phagosome

36
Q

Coley’s toxins (1900-1910)

A

observed spontaneous recovery from bacterial infection?

developed concoction from bacterial cells

37
Q

adaptive recognition

A

adaptive immune cells recognise antigens that are unique to an individual pathogen

38
Q

common types of bacterial antigens on surface of bacterial cell

A

proteins

polysaccharides

39
Q

2 MHC presentational pathways

A

protein escapes phagosome into cytosol

protein taken up into pahgosome

40
Q

if protein antigen escapes phagosome …

A

antigen enters cytosol
proteins recognised and processed in the proteasome
proteins complexed with MHC I
fragments presented to and recognised by CD8+ T cells

41
Q

if protein antigen is taken up into phagosome

A

protein is killed and processed inside phagosome by endocytosis of extracellular protein
complexed with MHC II
antigen fragments presented to and recognised by CD4+ T cells

42
Q

role of CD8+ T cells

A

activated and kill host infectected cells by releasing toxins

43
Q

toxins released by CD8+ T cells

A

perforin
granzymes
granulysin

44
Q

CD8 T cells are critical during which two infections

A

tuberculosis

salmonellosis

45
Q

role of CD4+ t cells

A

activate immune system

promote cytokine production

46
Q

effects of cytokine production due to activation of CD4+ T cells

A

macrophage activation
inflammation
maturation of antibody response

47
Q

role of CD4+ t cells

A

activate immune system

promote cytokine production

48
Q

effects of cytokine production due to activation of CD4+ T cells

A

macrophage activation
inflammation
maturation of antibody response

49
Q

4 protective mechanisms of antibodies

A
  1. complement pathway activation
  2. agglutination
  3. neutralisation
  4. opsonisation
50
Q

how do antibodies activate complement

A

antibodies bound to bacteria form complexes with antigens

classical pathway

51
Q

how do antibodies protect the body using agglutination

A

antibodies cause bacteria to stick together and clump allowing more effective cleaning by phagocytes

52
Q

importance of neutralisation caused bby antibodies

A

defends cell from antigen

neutralises cells effect eg. the toxins

53
Q

example of a neutralising antibody

A

diptheria antitoxin

neutralises biological effects of diptheria toxin

54
Q

effect of antibodies against streptococcal pneumonia

A

antibodies cause agglutination, opsonisation and activation of complement

55
Q

effect of antibodies against tetanus

A

antibodies neutralise toxin

cellular basis of immunity (21 decks)

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