Microbiology 4 Flashcards
Innate immunity
body’s first line of defense
non-specific
provides instantaneous response
Adaptive (acquired) immunity
2nd line of defense
used when innate immunity fails
highly specific: developed after exposure
conferred by our immune system: antibody and cellular responses
has memory
External physical barriers
intact skin
mucous membranes and secretions
ciliated epithelial cells
Intact skin
provides impenetrable barrier to pathogens
Mucous membranes and secretions
in the GI, respiratory and urogenital tracts
trap pathogens
Cilliated epithelial cells
sweep mucous entrapped microbes out of the system
External chemical barriers
Enzymes
Digestive secretions
Enzymes
sweat, saliva and tears
contain lysozyme
Digestive secretions
stomach acid
chemically inactivates the pathogen
Internal defensive factors
phagocytosis natural killer cells inflammation fever complement system interferon
Phagocytosis
cellular defense
neutrophills, monocytes and macrophages eat virus infected cells
Phagocytosis processes
chemotaxis
adherence
ingestion
digestion
Phagocytosis: chemotaxis
movement of cells toward a chemical stimulus
Uses chemotactic chemicals and cytokines
Chemotactic chemicals
microbial products or damaged tissue cells that attract phagocytes
Cytokines
chemicals released by phagocytes that have diverse functions
Chemokines
a class of cytokine attract phagocytes to the site of infection
Phagocytosis: adherance
the ability of the phagocyte to bind to molecules on the surface of the microbe
toll-like receptors on phagocyte recognize bacterial cell components
pathogens have anti-phagocytic capsule
Opsonization
the coating of microbes with serum proteins for optimal adherence of phagocytes
ex: antibodies or a complement protein
Phagocytosis: ingestion
phagocytes extend projections called pseudopods that engulf the microbe
once engulfed, the microbe is enclosed in the phagosome
enzymes pump protons into the phagosome and lower pH
hydrolytic enzymes are activated
Phagocytosis: digestion
phagosomes fuse with lysosomes to produce the phagolysosome
undigested material remains in the residual body of the lysosome and is excreted
Lysosome
digestive enzymes degrade microbes
defensins create holes in microbe membranes
oxidatively inactivate microbes by creating toxic oxygen “oxidative burst”
Natural Killer cells
cellular defense
produce non-specific lysis by apoptosis of cancer and virus infected cells
activity increased by interferon exposure
recognize surface glycoproteins on infected cells
NK cell process
secretion of cytotoxic proteins like perforin insert into plasma membrane of target cells and cause cell to burst “cytosis”
Inflammation
body’s response to colonization of damaged tissues by pathogens