Week 1 Practise Questions (L1-4)

Question 1

Why is innate immunity still important in higher organisms?

Answer 1

Immediate/rapid response, important before adaptive immunity develops. (Also usually needed to induce adaptive immunity).

Question 2

Why do we need adaptive immunity?

Answer 2

More specific (can adapt to changing pathogens), exhibits memory

Question 3

What do the terms “humoral” and “cell-mediated” immunity mean?

Answer 3

Corresponds to secreted antibody immunity (B cell derived) and T cell immunity (uses leukocytes)

Question 4

Describe some of the features of the lung epithelium that provide “barriers” to infection.

Answer 4

Many, but includes mucus (traps microbes), ciliated epithelial cells, tight junctions, defensins etc. in secretions

Question 5

Why do defensins have little activity against eukaryotic cells?

Answer 5

Bacteria have a greater transmembrane potential (more negatively charged inside) and defensins are cationic.

Question 6

What are the main pathways of complement activation?

Answer 6

Classical (requires antibody i.e. adaptive immunity), MB lectin, alternative (both innate)

Question 7

Describe two consequences of complement activation that help deal with a bacterial infection.

Answer 7

Activation of immune system (inflammation, induction of chemotaxis: C3a, C5a), opsonisation: (C3b), destabilisation of bacterial membranes (membrane attack complex)

Question 8

Why are host cells generally resistant to complement?

Answer 8

Express CD59 (membrane protein that stops formation of MAC)

Question 9

Why are tissue macrophages and mast cells described as “sentinel” cells?

Answer 9

Often the first to detect infection, because of where they’re sited

Question 10

How do eosinophils attack large parasites?

Answer 10

Release granule contents on the surface (toxic proteins, reactive oxygen and nitrogen species)

Question 11

What is “NETosis”?

Answer 11

A form of neutrophil death that releases DNA and chromatin impregnated with defensins etc., trapping microbes

Question 12

How do NK cells help deal with intracellular infections?

Answer 12

Induce apoptosis of infected host cells and can also directly kill some intracellular bacteria

Question 13

What are most important killing mechanisms in phagocytosis?

Answer 13

Reactive oxygen and nitrogen species produced following the oxidative burst