7. Phagocytes

Question 1

define pinocytosis

Answer 1

the engulfment of particles less than 0.5 um

Question 2

what particle does phagocytosis depend on

Answer 2

actin

Question 3

define phagocytosis

Answer 3

actin-dependent engulfment of particles LARGER than 0.5 um

Question 4

what is phagosome maturation

Answer 4

the process by which particles enter membrane bound structures before they are degraded

Question 5

what are the main feeders on biofilms

Answer 5

amoebae

Question 6

what must macrophages process before an immune response can be launched

Answer 6

process antigens and present them on the surface

Question 7

what do PAMPs stand for

Answer 7

pathogen-associated molecular patterns

Question 8

what have PAMPs

Answer 8

bacteria

Question 9

give 3 example of PAMPs

Answer 9

adhesins (pili, fimbrae)
O-antigens of LPS
peptidoglycan

Question 10

what are the two types of receptors used by phagocytes to bind to their prey

Answer 10

toll-like receptors (TLRs)

Pattern recognition receptors (PRRs)

Question 11

what type of receptors do amoebae have

Answer 11

pattern recognition receptors

Question 12

how do toll-like receptors work

Answer 12

start a cascade that activates the phagocyte

Question 13

how do pattern recognition receptors work

Answer 13

binding to these glycoproteins on the phagocyte surface directly induce phagocytosis

Question 14

how can bacteria avoid ingestion

Answer 14

• altering their PAMPs
• using defensive virulence factors
• using offensive virulence factors

Question 15

how do bacteria change their PAMPs

Answer 15

antigenic variation to the sugar moiety, until they become unrecognisable

Question 16

give an example of variation to PAMPs

Answer 16

acetylation or glycolysation of peptidoglycan = unrecognisable to phagocytes

Question 17

name a defensive virulence factor

Answer 17

being encapsulated

Question 18

name an offensive virulence factor

Answer 18

production of leukocidins

Question 19

how do leukocidins work

Answer 19

produce cytotoxins that kill phagocytes

Question 20

how do pathogens avoid digestion?

Answer 20

1. tolerance ( shock response)
2. avoidance (interfere with digestion
3. escape (leave vacuole and divide)

Question 21

describe the ‘shock’ response bacteria experience when they enter the phagosome

Answer 21

produce stress proteins called ‘chaperonins’

these re-fold incorrectly folded polypeptides

Question 22

what specific molecules are used to refold polypeptides in e.coli

Answer 22

DnaK

Question 23

why is it important that incorrectly folded polypeptides are refolded

Answer 23

the more stressed the bacteria - the more folding mistakes are made

this allows them to tolerate the digestive process

Question 24

how do pathogens interfere with digestion

Answer 24

produce a protease that disrupts the host superoxide anion generation

Question 25

how can pathogens escape digestion

Answer 25

leave the food vacuole and divide in the host cytoplasm before eventually bursting the cell