Lecture 28 - Host/Pathogen Interactions Flashcards
How does LPS endotoxemia lead to septic shock?
LPS is released when gram-negative bacteria are lysed. It binds to LBP, interacts with macrophages, which releases cytokines.
Blood is lost to tissues, and hypovolemia causes organ failure and death.
How is LPS detected in medical preparations that are injected into a patient?
Use limulus amoebocyte lysate (LAL) assay
Coagulation in presence of LPS
Endotoxin vs Exotoxin
Exotoxin:
secreted
protein based, often A-B type
high toxicity
Endotoxin:
part of cell (outer membrane)
lipid A of LPS
causes fever
Heat stable
medium toxicity
Why is it hard to develop a vaccine against endotoxin?
Mechanism of action of a bacterial A-B toxin
B binds to receptor
A part is toxic
Types of A-B toxins
Protective antigen:
Lethal Factor
Edema Factor
How does anthrax toxin kill intoxicated cells?
lethal factor is endocytosed
What are two types of cellulolytic toxins?
hemolysins
phospholipases
Differentiate between alpha beta hemolysins
alpha hemolysin: acts as a pore complex, impacts iron in rbc’s
beta hemolysis: lyse rbc’s
How do phospholipases kill cells?
removes polar head group on phospholipids, disrupts membranes
What are two types of tissue damaging toxins
exfoliative toxin
hyaluronidase
How do hyluronidases allow bacteria to spread to deep tissues
break down hyaluronic acid and connnective tissue of dermis
What is the mode of action of superantigen toxins
activates Th cells by crosslinking it to MHCII regardless if an antigen is present.
massive T cell activation leads to toxic shock
Name a superantigen toxin
Toxic shock syndrome toxin (TSST)
Name two infections in which the main damage is cause by inflammation
meningitis
pelvic inflammatory disease (PID)
Know the phenomenon of induced autoimmune disease
antibodies for Strep M protein also recognize autoantigen on heart muscle
What is a disease caused by immune mimicry
rheumatic heart disease
What are four ways viruses can avoid inactivation by the immune system
- produce IFN repressors (cannot signal neighboring cells)
- produce p53 inhibitors (inhibit apoptosis)
- produce MHC analog (reverses NK-mediated killing)
- Produce proteins that stop/reverse MHCI antigen presentation pathway
What are some funal toxins?
aflotoxin
ergot poisoning
Which type of fungal infection is most serious
dimorphic fungi, which can be mold in cool temperatures or yeast in warm temperatures
What are three examples of protozoal avoidance of the immune system?
