Immunology 1

Question 1

Define pathogen

Answer 1

A microorganism that causes disease when it infects a host

Question 2

Define zygomen

Answer 2

Inactive form of an enzyme, usually protease. Modified to become active

Question 3

Define chemokine

Answer 3

A small chemoattractant protein that stimulates the migration and activation of cells

Question 4

Define cytokine

Answer 4

A small protein affecting behaviour of other cells - if secreted by lymphocytes, they’re called interleukins

Question 5

What are the layers of defence as the pathogen attacks

Answer 5

Layer 1 - Physical (skin, hair)
Layer 2 - Soluble factors (breathe in)
Layer 3 - Innate arm (first response to pathogen)
Layer 4 - Adaptive arm (secondary response)

Question 6

What barriers to infection do surface epithelia provide (layer 1 - physical)

Answer 6

• Mechanical
• Chemical
• Microbiological

Question 7

Describe layer 2 (soluble factors)

Answer 7

• Bacterial walls contain peptidoglycan (polymer of 2 sugars)
• Lysozymes in saliva are most active against gram +ve bacteria as they break the beta 1-4 glycosidic bond - exposes lipid bilayer of bacterial membrane to other antimicrobial agents

Question 8

What are defensins?

What do defensins do?

Answer 8

• Short, cationic peptides
• Insert into membrane and generate pores so membrane becomes leaky

Question 9

What are cathelicidins?

What do cathelicidins do?

Answer 9

• Peptides that don’t contain disulphide bonds
• In neutrophils, they’re only activated when needed
• Amphipathic
• Carboxy-terminal peptide disrupts membrane

Question 10

What are histatins?

What do histatins do?

Answer 10

• Peptides produced by parotid, submandibular and sublingual salivary glands
• Active against pathogenic fungi (e.g. yeast)

Question 11

What is the difference between the innate arm and adaptive arm in terms of:
- Response speed
- Recognition of self (host) and non-self (pathogen)
- Lasting protection/memory

Answer 11

Question 12

What are the stages of the compliment system

Answer 12

1. Activation occurs on surfaces e.g. bacterium surface
2. Pattern recognition receptors of antibodies detect the antigen pathogen
3. Antibodies activate the initial zymogen
4. Creates a cascade of proteolysis where complement zymogens become proteolytically cleaved + activate many molecules of the next zymogen in the pathway
5. Therefore, even if small numbers of pathogens are detected, a rapid response is produced