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Phase 1 > Bacteria and Immune Response > Flashcards

Bacteria and Immune Response Flashcards

1
Q

what is the general structure of a prokaryote? (6)

A
  • no membrane-organelles
  • genetic information carried in double stranded circular molecule of DNA (nucleoid)
  • extrachromasomal DNA in plasmids
  • 70s ribosomes
  • prokaryote membrane (carries out other metabolic functions)
  • most have a complex cell wall
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2
Q

what are 3 structures that are present on some bacteria but not others? what are their functions?

A
  • capsule - adhesion, fluid absorption, protection from phagocytes
  • flagella - movement, ie. chemotaxis
  • pilli - common pilli attach to host cell membrane molecules, sex pilli allow horizontal gene transfer
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3
Q

what is the difference between the cell walls of Gram+ and Gram- bacteria?

A
  • G+: thick layer of peptidoglycan, teichoic acid anchors

* G-: thin layer of peptidoglycan, overlaid by outer membrane which is anchored by lipoproteins

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4
Q

what may cause a bacteria to be Gram-variable or Gram stain unreliable? (3)

A
  • too small
  • no cell wall
  • atypical life cycle
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5
Q

what are the 3 main bacteria shapes?

A
  • cocci - spherical
  • bacilli - rod
  • spirilla - helical
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6
Q

what are the 5 steps of Gram staining?

A

1 - fixation: eg. via heating
2 - crystal violet: complexes with peptidoglycans - stains +ve cells (-ve cells will appear purple at this point)
3 - iodine: allows CV to complex in +ve cells
4 - decolourisation: using acetone / alcohol solvent (-ve cells decolourised)
5 - counter-stain: safranin stains -ve cells pink

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7
Q

what are 2 examples of G+ cocci?

A
  • Staphylococcus aureus

* Streptococcus pneumoniae

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8
Q

what are 2 examples of G+ bacilli?

A
  • Listeria monocytogenes

* Corynebacterium diphtheriae

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9
Q

what is an example of a G- cocci?

A

Neisseria meningiditis

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10
Q

what are 2 examples of G- bacilli

A
  • Escherichia coli

* Salmonella species

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11
Q

describe the growth pattern of bacteria when introduced to a new environment (4)

A

lag-log

1 - initial lag: period of adjustment
2 - log: cell division occurs rapidly, exponential growth
3 - stationary: nutrients have depleted / toxins have built up
4 - death: enters a phase of decline

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12
Q

how do prokaryotes replicate their DNA?

A

unwinding of DNA, then each strand serves as a template for DNA polymerase

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13
Q

describe the process of conjugation in bacteria (2)

A

1 - a gene in conjunctive plasmids tell the cell to produce a sex pilus and replicate itself
2 - cytoplasmic bridge forms between 2 cells and allows conjunctive plasmid to be transferred

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14
Q

what are commensal bacteria?

A

bacteria that are not infectious and act as part of the body’s natural flora

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15
Q

what are 4 functions of commensal bacteria?

A
  • out-compete pathogenic bacteria for space and resources
  • produce by-products that prevent pathogen establishment
  • vitamins in gut are synthesised as end-products
  • stimulate immune system
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16
Q

where are the major flora communities? what are areas of the body with no bacteria in them called?

A
  • skin
  • mouth
  • large intestine
  • urinary tract
  • vaginal tract

sterile body sites

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17
Q

what are the 2 causes of bacterial infection?

A
  • commensal bacteria invades a sterile site

* pathogenic bacteria enter the body (non-commensal)

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18
Q

how can an infection be picked up? (3)

A
  • translocation from non-sterile to sterile areas
  • acquisition from animals / other humans
  • transmission from the environment
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19
Q

in what circumstances might an opportunistic infection be picked up? (3)

A
  • weakened immune system (eg. AIDS)
  • reduced flora community (decrease in competition)
  • breached surface barriers
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20
Q

what is a nosocomial infection?

A

an infection acquired while a patient is in hospital

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21
Q

what is a carrier?

A

an organism / individual that can transmit the pathogen but does not experience symptoms (transient or chronic)

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22
Q

what the 2 mains types of toxins produced by bacteria?

A
  • endotoxins (mainly G-): released after host cell lysis

* exotoxins (mainly G+): secreted from cell surface, dangerous as they can cause toxic shock syndrome

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23
Q

what factors affect infection? (6)

A
  • age, sex, ethnicity, diet
  • medical conditions / medication
  • immunocompromised
  • presence of foreign objects (bio films)
  • vaccination history
  • crowding, seasonal variation and public health measures
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24
Q

what is the natural course of infection? (7)

A

1 - entrance through breach of defences / barriers
2 - colonisation: adherence, adhesion, attachment
3 - multiplication and spread through the body
4 - invasion of host cells
5 - signs and symptoms: based on virulence and immune response
6 - resolution or chronic state occurs
7 - elimination / exit of pathogen

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25
Q

what is a common infection of the respiratory system? what pathogens cause it? (2)

A

pneumonia

  • Steptococcus pneumoniae
  • Haemophilius influenza
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26
Q

what is a common infection of the gastrointestinal system? what pathogens cause it? (4)

A

food poisoning

  • Campylobacter
  • Salmonella
  • some E. coli
  • Shingella
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27
Q

what is a common infection of the CNS? what pathogen causes it?

A

meningitis

• Neisseria meningitis

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28
Q

what is a common infection of bones / joints? what pathogen causes it?

A

osteomyelitis

• Staphyloccocus aureus

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29
Q

what is a common infection of the skin / soft tissues?

A

cellulitis

• Staphylococcus aureus

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30
Q

in what scenarios would an infection require empiric rather than targeted treatment? (7)

A
  • infection of sterile site
  • meningitis, CNS infection, cerebral abscess
  • septic arthritis
  • deep ocular / periorbital infections (eye socket)
  • infections involving breach of the GI tract
  • any outbreak scenarios / public health risk
  • any infection in which the patient is septic
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31
Q

what characterises sepsis? (3)

A
  • systematic loss of homeostasis + dysfunction of each organ
  • physiological demand requires increased cardiac output (tachycardia)
  • capillary leakage of plasma leading to tissue oedema
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32
Q

what are 4 lab tests used in the identification of bacteria?

A
  • latex agglutination - find out antigens
  • indicator antibiotics
  • selective / differential media (eg. stool sample - only salmonella can grow on medium, commensal bacteria cannot)
  • chromogenic agar plate - automated with computer
33
Q

what are the main differences between the innate and adaptive immune systems?

A
  • innate: born with it - operates throughout life

* adaptive: changes in response to the pathogens it encounters

34
Q

what are 2 features of the neutrophil cell?

A
  • multi-lobed nucleus

* granular

35
Q

where are neutrophils found outside of infection?

A

in blood circulation

36
Q

in what 2 conditions do neutrophils undertake phagocytosis?

A
  • direct contact with bacteria

* after bacteria have been opsonised

37
Q

what 2 factors can be found in the granules of a neutrophil?

A
  • bacteriostatic factors

* toxic factors

38
Q

as well as phagocytosis? what other main function do neutrophils have?

A

release chemokines and cytokines

39
Q

how are neutrophils directed to where a bacteria is?

A
  • other cells release chemotactic factors

* move by chemotaxis towards bacteria

40
Q

what must happen before neutrophils can enter tissues to tackle infection? (3)

A
  • chemoattraction of neutrophil
  • rolling adhesion - neutrophil attach to endothelial cells
  • tight junctions are loosened
41
Q

what is the difference between a monocytes and a macrophage?

A

monocytes are in the blood, macrophages are in tissue

42
Q

what are 2 features of the monocyte cell?

A
  • large

* kidney shaped nucleus

43
Q

what is the function of macrophages? (4)

A
  • phagocytose pathogens
  • clear cellular debris
  • release cytokines and chemokines
  • act as APCs
44
Q

what is the main function of dendritic cells?

A

present antigens to T cells to activate the adaptive immune response

45
Q

what are the 3 pathways that initiate the compliment cascade?

A
  • classical - antigen:antibody complexes
  • alternative - pathogen surfaces
  • mannose-binding lectin: lectin -> pathogen
46
Q

what are the 3 main effects of complement?

A
  • inflammation - recruitment of inflammatory cells
  • lysis of pathogens
  • opsonisation - coating pathogens to make phagocytosis easier
47
Q

what happens to T cells in the thymus? (2)

A
  • maturation - acquire repertoire

* auto reactive cells are deselected

48
Q

where do T cells travel to after leaving the thymus?

A

secondary lymphoid organs - spleen and lymph nodes

49
Q

how are Th cells activated?

A
  • a dendritic cell or macrophage with MHC call 2 presents pathogen antigen on cell surface
  • travels to lymphoid organs
  • the T cell corresponding to the pathogen complexes to the antigen and is activated
50
Q

what are the effects of Th activation? (4)

A
  • clonal expansion
  • some differentiate into memory cells
  • activate humoral response
  • activate cytotoxic T cells
51
Q

how are cytotoxic T cells activated? (4)

A
  • signal from Th cell activates the Tc cell
  • body cell infected with pathogen will present its antigen on cell surface using MHC class 1
  • binds to the TCR on Tc cell
  • Tc cell then causes apoptosis
52
Q

how do cytotoxic T cells cause apoptosis? (3)

A
  • release perforin and granzymes when T cell attaches to cell receptor
  • perforin creates a tube between cells
  • granzymes enter and trigger apoptosis
53
Q

what are membrane-bound immunoglobulins? (2)

A
  • on B cell surface

* act as antibody and receptor

54
Q

what happens after a B cell is activated?

A
  • clonal expansion
  • differentiation into plasma cells
  • release antibodies
55
Q

what are the 3 most significant types of antibodies? give their shape and function

A
  • Ig A - dimer, involved in mucosal immunity
  • Ig D - monomer, native B cell receptor
  • IgM - pentamer, made first, antigen receptor and involved in complement activation
56
Q

what are 3 modes of antibody action on pathogens?

A
  • neutralisation - clump bacteria, easier for phagocytosis
  • opsonisation
  • complement activation
57
Q

what are the 2 goals of inflammation?

A
  • expel foreign body / infection

* cause structural and functional repair

58
Q

what are the 5 characterisations of inflammation? what causes these signs?

A
  • heat (calor) - vasodilation
  • redness (rubor) - increased blood flow (vasodilation and fever)
  • swelling (tumor) - fluid in extracellular matrix
  • pain (dolor) - stretching of tissue (oedema), mediators stimulate pain receptors
  • loss of function (function laesa) - inhibited by pain and swelling
59
Q

what are 3 positive aspects of inflammation?

A
  • isolates damaged area
  • mobilises effector cells / molecules
  • promotes healing and repair
60
Q

what are 3 negative aspects of inflammation?

A
  • response may be out of proportion to threat
  • may cause more damage to body than agent would have
  • chronic inflammation (eg. allergies / autoimmune conditions)
61
Q

what must inflammation do to localise inflammatory cells and molecules? (2)

A
  • exudate fluids and proteins

* concentrate cells of blood in damaged tissue using cytokines

62
Q

what happens during the initiation stage of inflammation? (3)

A
  • changes in microvasculature
  • extravasated - discharge of blood into tissues
  • leukocytes emigrate across tight junctions into tissues
63
Q

what happens at the progression phase of inflammation?

A

cytokines and cellular inflammatory systems are activated and amplified

64
Q

what happens in the resolution phase of inflammation?

A

specific inhibition and dissipation of cytokines / mediators

65
Q

how do neutrophils perform phagocytosis? (2)

A
  • isolates pathogen in phagocyte

* granules containing digestive / destructive enzymes fuse with phagosome and destroy pathogen

66
Q

what are Toll-like receptors, PAMPs, and DAMPs? which cells have Toll-like receptors?

A
  • TLRs bind to PAMPs and DAMPs to induce a response from the leukocyte cell
  • PAMPs (pathogen associated molecular patterns) are expressed by bacteria on their cell surface, and allow leukocytes to recognise them as dangerous
  • DAMPs (damaged associated molecular patterns) are expressed by cells what are dying (or tumour cells) - not always associated with infection

• mostly innate immune cells - macrophages, monocytes and dendritic cells (also sometimes fibroblasts and epithelial cells)

67
Q

how do macrophages perform phagocytosis?

A

fuse phagosome with lysosome (rather than granules)

68
Q

describe how lymph leaves the blood and enters the lymphatic system (5)

A

1 - fluid moved out of capillaries at arteriole end due to hydrostatic pressure
2 - (most) proteins and blood cells remain inside, so blood becomes more concentrated in the capillary
3 - osmotic pressure draws fluid back into circulation at venue end
4 - some proteins do escape however, and allow some fluid to be retained in tissues
5 - blind ending lymphatic capillaries draw excess fluid and proteins from tissue into lymphatics

69
Q

what condition is causes by a failure of the lymphatic system to reabsorb fluid from tissues? what are some common causes? (3)

A
  • lymphoedema

* usually caused by lymph node damage after an accident, surgery or radiotherapy

70
Q

what are the 2 ways in which lymph can enter the lymphatic capillary?

A
  • flow into lumen through gaps between specialised epithelium (valve)
  • absorbed by plasma membrane via pinocytosis and then released in lumen
71
Q

how is the lymphatic capillary held open?

A

anchoring filaments

72
Q

what is the route of lymph after it enters at the capillary? (5)

A
  • increasingly larger lymphatic vessels
  • through lymph nodes
  • collecting ducts
  • lymphatic trunk
  • either the right lymphatic duct or the thoracic duct
73
Q

what parts of the body does the right lymphatic duct and thoracic duct drain from?

A
  • RLD - upper right limb and above (right side)

* thoracic - lower limbs, upper left limb and above (left side)

74
Q

where does lymph re-enter circulation? why here?

A
  • subclavian veins running beneath collar bones

* blood is under the lowest pressure here

75
Q

other than lymphocytes, what other leukocytes are found in the lymph node?

A

macrophages, dendritic cells

76
Q

what is the function of reticular tissue in the lymph node?

A

connective tissue acting as stroma

77
Q

in what parts of the lymph node are T, B and dendritic cells housed?

A
  • B cells - cortex follicles

* T cells + dendritic cells - paracortex

78
Q

what are the primary lymphoid organs? what are the secondary lymphoid organs? what are their broad functions?

A
  • 1º - bone marrow and thymus
  • generate lymphocytes
  • 2º - lymph nodes and spleen
  • maintain native lymphocytes and initiate adaptive immune response

Phase 1 (14 decks)

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