7. Phagocytes Flashcards
define pinocytosis
the engulfment of particles less than 0.5 um
what particle does phagocytosis depend on
actin
define phagocytosis
actin-dependent engulfment of particles LARGER than 0.5 um
what is phagosome maturation
the process by which particles enter membrane bound structures before they are degraded
what are the main feeders on biofilms
amoebae
what must macrophages process before an immune response can be launched
process antigens and present them on the surface
what do PAMPs stand for
pathogen-associated molecular patterns
what have PAMPs
bacteria
give 3 example of PAMPs
adhesins (pili, fimbrae)
O-antigens of LPS
peptidoglycan
what are the two types of receptors used by phagocytes to bind to their prey
toll-like receptors (TLRs)
Pattern recognition receptors (PRRs)
what type of receptors do amoebae have
pattern recognition receptors
how do toll-like receptors work
start a cascade that activates the phagocyte
how do pattern recognition receptors work
binding to these glycoproteins on the phagocyte surface directly induce phagocytosis
how can bacteria avoid ingestion
- altering their PAMPs
- using defensive virulence factors
- using offensive virulence factors
how do bacteria change their PAMPs
antigenic variation to the sugar moiety, until they become unrecognisable
give an example of variation to PAMPs
acetylation or glycolysation of peptidoglycan = unrecognisable to phagocytes
name a defensive virulence factor
being encapsulated
name an offensive virulence factor
production of leukocidins
how do leukocidins work
produce cytotoxins that kill phagocytes
how do pathogens avoid digestion?
- tolerance ( shock response)
- avoidance (interfere with digestion
- escape (leave vacuole and divide)
describe the ‘shock’ response bacteria experience when they enter the phagosome
produce stress proteins called ‘chaperonins’
these re-fold incorrectly folded polypeptides
what specific molecules are used to refold polypeptides in e.coli
DnaK
why is it important that incorrectly folded polypeptides are refolded
the more stressed the bacteria - the more folding mistakes are made
this allows them to tolerate the digestive process
how do pathogens interfere with digestion
produce a protease that disrupts the host superoxide anion generation
