9. When cancer goes wrong

Question 1

What are the signalling molecules in signalling pathways commonly attacked by? and what do these do?

Answer 1

pathogens manipulate pathways to influence cell host survival e.g. during an infection

Question 2

State 2 toxins used by pathogens to hijack cell host machinery for their own benefit

Answer 2

Cholera toxin and pertussis toxin released into cytoplasm e.g. by forming pore channels or through receptor-mediated endocytosis

Question 3

what is the mode of transport used by Vibrio cholerae? what is the infectious dose?

Answer 3

1. water (infectious dose; 10^9)
2. food (infectious dose 10^3)
   note; cholera is resistant to heat and freezing

Question 4

Steps of entry of bacterium into host

Answer 4

1. entry via ingestion
2. colonisation (of epithelial lining of small intestine
3. disease e.g. diarrhoea, vomiting, acidosis
4. exit (litres of water/day)

Question 5

What induces the symptoms of cholera?

Answer 5

Toxins - cholera toxin CTX

Question 6

List 6 features of Vibrio Cholerae

Answer 6

• Gram -negative bacterium
• Flagella
• 2 chromosomes
• Asporogenous (doesn’t form spores)
• Curved rod
• Ferments Gluclose, Sucrose and Mannitol

Question 7

What allows the bacteria to colonise?

Answer 7

They are packed with virulence factors within the 2 chromosomes

Question 8

What is Homeostasis? This is driven by what cells?

Answer 8

maintaining stable equilibrium - by passage via large colon and removal of water products from the intestines. this is driven by crypt cells which activately secrete electrolytes, leading to water secretion

Question 9

Describe how water is secreted by crypt cells.

Answer 9

Cl- ions flow through channel, different stimuli activate the GCPR receptor (CFTR), activating adenylyl cyclase, generating cAMP (secondary messenger). This results in the secretion of Cl- ions in the lumen of the large colon, an electrical potential is produced attracting Na+n ions, drawing water into the gut.

Question 10

What receptor allows the passage of Cl- ions into the intestinal lumen?

Answer 10

CFTR

Question 11

What can disturb the water secretion process?

Answer 11

Toxins - diarrhoea - loss of water

Question 12

State features of Bordetella Pertussis (whooping cough) and what causes it?

Answer 12

• Gram-negative bacterium, aerobic, encapsulated bacterium which stick to cilia in the respiratory tract causing the whooping cough.

Question 13

How is Bordetella Pertussis transmitted?

Answer 13

person-person via respiratory droplets

Question 14

What pathogen secretes Pertussis PTX?

Answer 14

Bordetella Pertussis

Question 15

During water secretion, how do Na+ ions enter the lumen? what does this result in?

Answer 15

enter via tight junctions, resulting in NACL, generating an osmotic gradient drawing water into the gut lumen.

Question 16

In somatic cells, what do JAK-STAT mutations lead to? what is this caused by?

Answer 16

cancer caused by damage to DNA etc. by UV radiation, reactive oxygen species..

Question 17

In germ cells, what do JAK-STAT mutations lead to? what is this caused by?

Answer 17

Primary immunodeficiency caused by inherited mutations

Question 18

what is JAK-STAT signalling?

Answer 18

cytokine receptor signalling

Question 19

What is x-linked SKID?

Answer 19

a primary immunodeficiency caused by mutations in germ cells inherited by either the mother or father. The individual will have a low number of T-cells and the loss of 2 immune cells (T cells and B cells) which become non-functional

Question 20

What is x-linked SKID caused by?

Answer 20

many different mutations on the common gamma gene on the x-linked chromosome and so usually only affect males

Question 21

How is x-linked SKID treated?

Answer 21

bone marrow transplantation

Question 22

How is the development and function of T cells and B cells impacted?

Answer 22

• absence of the common gamma chain
• cells cannot respond to cytokines which bind to receptors that use this shared component.
• JAK 3 gene has the same biological impact