Lecture 7

Question 1

What are bacterial superantigens

Answer 1

• Proteins that act indirectly on host cells

Question 2

What do bacterial superantigens do?

Answer 2

Stimulate T-cell overproduction after bind Vbeta region of TCR

Question 3

What percentage of T-cells do superantigens activate?

Answer 3

5-25%

Question 4

What percentage of T-cells do normal antigens activate?

Answer 4

0.05%

Question 5

What do T-cells produce?

Answer 5

Cytokines that overproduce IF-Y-

Macrophages activate to overproduce more cytokines, IL-1, IL-6, TNF-a

Leads to inflammation, shock, organ failure

Question 6

Explain toxic shock syndrome

Answer 6

Staphylococcus aureus toxic shock syndrome toxin 1 (TSST1)

Secretion of fluids and electrolytes reduces blood volume and pressure

Question 7

Qualities of TSST1

Answer 7

Very resistant to proteases
Stable at 60 degrees Celsius
Can survive pH 2.5-11

Question 8

How can you be exposed to toxins?

Answer 8

Intoxication - Uptake of pre-formed toxin e.g. C. botulinum toxin or Staphylococcal enterotoxins

Colonisation and in situ toxin production - C. perfringens, Salmonella spp. E. coli

High density of pathogens required for biofilm formation and toxin production

Question 9

Siderophores

Answer 9

Animals and plants require iron for metabolism and growth

Animals withhold iron from tissue fluids by binding it to haemoglobin, transferrin, or lactoferrin

Pathogens normally access ion in haemoglobin

Low conc of iron - Synthesis of siderophores by pathogen

Question 10

What does DTxR in Corynebacterium diphtheriae do?

Answer 10

As well as control express of tox gene, it contains genes for siderophore production