Chapter 9 - Bacteria Flashcards
what does cell membrane damage cause
cell death
damage is proportional to _____
number of bacteria inside cell
how are host cells lysed using cell mediated immuntiy
CTL activation uses perforin and granzymes to kill cells displaying MHC class I
what are the mechanisms of cell death
-growth of pathogen within host cells
- cell- mediated immunity
- membrane damaging toxins - apoptosis
what is uncontrolled inflammation due to
exaggerated adaptive immune responses = hypersensitivities
what is involved in a health inflammation response
-increased blood supply (redness)
- increased vascular permeability (edema)
- chemotaxis (infiltration by phagocytes and lymphocytes)
what is type I hypersensitivity
allergy but can lead to anaphylaxis and shock
what is type II hypersensitivity
bound antibodies leading to complement and leukocyte activation to surfaces
what is type III hypersensitivity
bound antibodies leading to complement and leukocyte activation to soluble molecules then immune complex deposition
what is type IV hypersensitivity
inflammation by purely CMI responses not antibodies
what are toxins
microbial product or component that can injure another cell or organism at low concentrations
what ways do toxins act
- modulation of targets inside a host cell
- action on surface of a host cell
- action in the ECM
where are toxin encoding genes carried
on plasmids or temperate bacteriophage genomes
what proteins encode the proteins that make up cholera toxin
ctxA and ctxB
what are exotoxins secreted by
pathogens
- type I or type II secretion systems
what are type III cytotoxins injected into
host cells
-contact dependent
what are common features of exotoxins
-A-B toxins
-require activation (proteolysis or reduction of disulfides)
- many are ADP ribosyltransferases
what is the B domain
binding domain
what is the A domain
enzymatic domain
what does B domain mediate
the entry of the A domain into the host cell
what is diptheria toxin
an exotoxin
what is the mechanism of action of diptheria toxin
-A and B domains enter cell
- enters vesicle
- drop in pH separates A component from B component
- inhibits translocation reaction of protein synthesis
- cell death
what are examples of membrane damaging toxins
lipases, pore forming toxins, hemolysins
what acts on surface of a host cell
- membrane damaging toxins
- superantigens
-endotoxin
what is LPS of gram negative bacteria
endotoxin
what is the active toxin part of LPS
lipid A
what acts in the ECM
-exoenzymes
what are examples of exoenzymes
-collagenases, hyaluronidases, DNases
- streptokinase
what do exoenzymes do
help microbes spread
what does streptokinase do
activates plasminogen to convert to plasmin
how do you protect against exotoxins
-immunization with toxoids
- treatment with antitoxins “passive immunization”
