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22 Cards in this Set
- Front
- Back
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What are three ways of killing ingested pathogens
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1. non-oxidative killing
2. oxidative killing 3. reactive nitrogen killin |
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What are thre ways that pathogens prevent phagocytic killing?
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1. blocks phagocytosis
2. avoid lysosomal fusion 3. escape from vacuole/ phagosome |
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What is an example of a bacteria that blocks phagocytosis?
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S. pneumonia - uses capsule to prevent phagocytosis
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How does a capsule prevent phagocytosis?
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Prevents complement adherence so that macrophage cannot phagocytose
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How does non-oxidative killing of pathogens occur?
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acidification of phagosome, kills bacteria and allows some enzymes to work
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How does Yersinia block phagocytosis?
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Remains extracellular, but close to lymph - paralyses host molecules involved in phagocytosis - Type III effectors
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What are three ways pathogens avoid being killed?
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1. block phagocytosis
2. avoid lysosomal fusion 3. Escape from vacuole |
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Why do bacteria live intracellularly?
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- source of nutrients
- protection from immune system - protection from non-cell-penetrative abx |
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How does host overcome intracellular infection?
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Have T cells that lyse infected cells
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What are three ways bacteria can survive inside cells?
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1. can survive within phagolysosome (TB)
2. block fusion of phago with lyso 3. lyse out of phagosome (listeria) |
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How does Salmonella enterica survive?
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Intracellular, blocks fusion
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What are two salmonella serovars which are important pathogens?
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Typhi = typhoid fever
Typhimurium = gastroenteritis, restricted to endothelial layer |
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What are three steps to salmonella getting intracellular?
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- attachment - uses Type III effectors
- ruffling - stays in vacuole |
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What does Spy 1 do - salmonella?
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Activates actin so that it engulfs bacteria (opposite of Yersinia)
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What does Spy 2 do - salmonella?
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Makes vacuole a protected space - salmonella protected vacuole - where salmonella replicate
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How does M. tuberculosis evade host defences?
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- prevents fusion of phagosome with lysosome
- survives in acidified phagosome by defence factors - secretes and expresses proteins to arrest development of phagosome |
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How does TB get into cell?
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Interacts with cell membrane receptor to promote uptake
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What induces maturation of phagosome (related to TB)?
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Interferon gamma
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How does Listeria avoid host defences?
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Escape from vacuole, survives in cytoplasm and uses ActA to nucleate actin comet tail to exit cell
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How does Listeria escape from phagolysosome?
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Has a protein which degrades phagosome (LLO)
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How do cells use oxidative killing?
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H2O2, O2., OH. cause oxidative burst, and kill bacteria
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How do cells use nitrogen killing to prevent bacterial infection?
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Arginine metabolite NO is a poisonous gas
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