Immunology 9 - Host Defense Overview

Question 1

What are the surface receptors of the skin?

Answer 1

• The skin acts as a physical barrier
• Commensal bacteria outcompete the pathogens
• Chemical barriers such as mucus, acids and antimicrobial proteins

Question 2

List the mucosal surface defences.

Answer 2

• Coughing
• Sneezing
• Mucus
• Cilia
• Rapid cell turnover

Question 3

What are the sequential actions of the immune system?

Answer 3

• First line (avoidance, smell, taste, mucus, physical barriers, occurs pre-infection)
• Second line (phagocytes, opsoinins, interferons - type 1 innate immunity, occurs in early infection)
• Specific/acquired immunity (T cells and antibody in late infection)

Question 4

How does specificity, breadth and learning change through the immune response?

Answer 4

Specificity and learning increase, while the breadth decreases

Question 5

What are the types of interferons?

Answer 5

• Type I/III activates NK cells, increases MHC and induces an antiviral state.
• Type II are proinflammatory

Question 6

List the T cell subsets and their function

Answer 6

• Th1 are antiviral/bacteial
• Th2 used in allergy
• Th17 fungi/bacteria
• Tregs are regulatory

Question 7

List the defences against bacteria

Answer 7

• Surface defences
• Antibody opsonisation
• Phagocytosis
• Release of inflammatory mediators/acute phase proteins
• Fever

Question 8

List defences against viruses

Answer 8

• Surface defences
• Interferons
• Inflammatory mediators/acute phase proteins
• NK cells
• Antibody, complement
• T cells

Question 9

Describe the function of opsonins in simple terms

Answer 9

Opsonins cover pathogens to attract phagocytes - like covering chips in ketchup to make them more tasty.