Infection 3 Flashcards
Two types of immune response?
Innate and adaptive
What components of pathogen can the innate immune system recognise?
Peptidoglycan(cell wall), lipopolysaccharide, organelles like flagella
Types of innate immune cells?
Macrophages and polymorphonuclear lymphocytes, dendritic cells, mast cells, monocytes
What are examples of polymorphonuclear lymphocytes?
Neutrophils, basophils, eosinophils
Most common innate immune cells?
Macrophages and neutrophils
Which innate immune cell will be first encountered by a pathogen?
Macrophages
What cell type makes up the majority of white blood cells in the body?
Neutrophils
Where are macrophages found?
A wide variety of tissues in the body
What can macrophages do when they see a pathogen?
Recognise it as non-self
How do macrophages deal with an infection?
Attach to and engulf the pathogen, removing it from the tissue
Secrete cytokines
Role of cytokines that have been secreted by a macrophage?
Attract neutrophils and make the blood vessels “leaky”, and increase blood flow
How do neutrophils get to the site of the pathogen?
Follow a gradient of chemicals produced by the cytokines
Where are pathogens kept once inside a phagocyte?
A phagosome
What do phagosomes usually do?
Fuse with a lysosome–> contains lysozymes, proteases and defensins into the phagosome
Three main strategies to prevent bacterial cell death in a phagocyte?
Survive the phagosome-lysosome fusion
Break out of phagosome b4 lysosome fusion
Prevent fusion w/ lysosome
What does salmonella do once it has entered the body?
Enters a cell, and is encased into a salmonella containing vacuole (SCV)
How does salmonella survive once in he SCV?
The Salmonella Pathogenicity Island 2 (SPI2)
What does the SPI2 do?
Encodes functions that allow the pathogen to alter properties of the phagosome
Type 3 secretion system and effectors are injected into the cell through the phagosome membrane
Effects of SPI2 injecting things into the cell from the SCV?
Lysosome function is prevented
How does salmonella prevent lysosome binding to the phagosome?
Charge of the phagosome membrane is manipulated to the lysosome cant bind with it
How does salmonella time the transcription of the pathogenicity island right so they have the desired effect at the correct time?
Inside the vacuole the environment is diff to outside (pH, nutrient levels) and the bacteria detects these and can then change its gene expression accordingly
How does L. monocytogenes break out of a phagosome?
Senses the diff environment in the phagosome (more acidic (pH5.5)), and forms pores in the phagosome membrane
What pore forming toxin does L. monocytogenes encode?
Listeriolysin O (LLO)
What does L. monocytogenes do once free of the phagosome?
Polymerises the actin from the host cell to form a tail behind itself
Uses this to propel it through the cytoplasm
