Lecture 28 - Host/Pathogen Interactions

Question 1

How does LPS endotoxemia lead to septic shock?

Answer 1

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.

Question 2

How is LPS detected in medical preparations that are injected into a patient?

Answer 2

Use limulus amoebocyte lysate (LAL) assay
Coagulation in presence of LPS

Question 3

Endotoxin vs Exotoxin

Answer 3

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

Question 4

Why is it hard to develop a vaccine against endotoxin?

Question 5

Mechanism of action of a bacterial A-B toxin

Answer 5

B binds to receptor
A part is toxic

Question 6

Types of A-B toxins

Answer 6

Protective antigen:
Lethal Factor
Edema Factor

Question 7

How does anthrax toxin kill intoxicated cells?

Answer 7

lethal factor is endocytosed

Question 8

What are two types of cellulolytic toxins?

Answer 8

hemolysins
phospholipases

Question 9

Differentiate between alpha beta hemolysins

Answer 9

alpha hemolysin: acts as a pore complex, impacts iron in rbc’s
beta hemolysis: lyse rbc’s

Question 10

How do phospholipases kill cells?

Answer 10

removes polar head group on phospholipids, disrupts membranes

Question 11

What are two types of tissue damaging toxins

Answer 11

exfoliative toxin
hyaluronidase

Question 12

How do hyluronidases allow bacteria to spread to deep tissues

Answer 12

break down hyaluronic acid and connnective tissue of dermis

Question 13

What is the mode of action of superantigen toxins

Answer 13

activates Th cells by crosslinking it to MHCII regardless if an antigen is present.
massive T cell activation leads to toxic shock

Question 14

Name a superantigen toxin

Answer 14

Toxic shock syndrome toxin (TSST)

Question 15

Name two infections in which the main damage is cause by inflammation

Answer 15

meningitis
pelvic inflammatory disease (PID)

Question 16

Know the phenomenon of induced autoimmune disease

Answer 16

antibodies for Strep M protein also recognize autoantigen on heart muscle

Question 17

What is a disease caused by immune mimicry

Answer 17

rheumatic heart disease

Question 18

What are four ways viruses can avoid inactivation by the immune system

Answer 18

1. produce IFN repressors (cannot signal neighboring cells)
2. produce p53 inhibitors (inhibit apoptosis)
3. produce MHC analog (reverses NK-mediated killing)
4. Produce proteins that stop/reverse MHCI antigen presentation pathway

Question 19

What are some funal toxins?

Answer 19

aflotoxin
ergot poisoning

Question 20

Which type of fungal infection is most serious

Answer 20

dimorphic fungi, which can be mold in cool temperatures or yeast in warm temperatures

Question 21

What are three examples of protozoal avoidance of the immune system?