11.2 Innate Immunity

Question 1

Broadly, what can be found inside the granules of neutrophils?

Answer 1

• Enzymes
• Antimicrobial peptides

Question 2

What is granulopoiesis?

Answer 2

Production of granulocytes

Question 3

Name one cytokine that drives granulopoiesis

Answer 3

Granulocyte-colony simulating factor (G-CSF)

Question 4

List and described the three functions of neutrophils

Answer 4

1. Phagocytosis: (ingestion, release of granules to destroy phagosome contents)
2. Degranulation: (release of granule contents into external environment)
3. Netosis: (expulsion of nuclear material to form neutrophil extracellular traps (NETs)

Question 5

How do NK cells kill?

Answer 5

• Apoptosis
• Victim cell forms into blebs, which can be removed by neutrophils or macrophages

Question 6

Are dendritic cells capable of endocytosis, phagocytosis, or both?

Answer 6

Both; think about it: it needs to bring the sample into the cell, and break it down for presentation

Question 7

With regards to surface receptors, under what circumstances would an NK cell/not kill a cell?

Answer 7

It would only kill if the activating receptor is activated, and the inhibitory receptor is not. All other circumstances, no killing of the cell

Question 8

Describe degranulation of NK cells; what is released?

Answer 8

1. Release perforins, which create channels for…
2. Granzymes, which cause apoptosis

Question 9

Describe the collectrin family of proteins?

Answer 9

• Contain six recognition domains which bind to microbe surface carbohydrates
• Contain a collagen-like region, which is recognised by phagocytes

Question 10

What are some examples of opsonins from the collectin family?

Answer 10

• Surfactant protein
• Mannose binding lectin

Question 11

Describe the pentraxin family of opsonins

Answer 11

• FIVE polypeptides
• Bind to bacteria-specific structures

Question 12

Give an examples of a pentraxin opsonin

Answer 12

C Reactive Protein

Question 13

Which type of PRRs detect DAMPs?

Answer 13

Scavenger receptors

Question 14

Which CD surface protein means “don’t eat me”!

Answer 14

CD47

Question 15

Which protein flips from inside to outside the cell during apoptosis, and is detected by macrophage PRRs?

Answer 15

Phosphatidyl serine

Question 16

Are opsonins antibodies?

Answer 16

• No
• But antibodies are opsonins; it’s one of their functions

Question 17

Broadly, what are the two classes of recognition that can trigger apoptosis

Answer 17

• Direct recognition (through PRRs)
• Indirect recognition (through opsonin receptors)

Question 18

What happens once a PAMP binds to a PRR?

Answer 18

• Adaptor molecule at the base of the PRR is activated
• Triggers release of transcription factors
• Triggers production of cytokines
• Leads to innate immune response

Question 19

Where are complement proteins made?

Answer 19

• Liver hepatocytes
• Blood monocytes
• Tissue macrophages
• GI epithelium

Question 20

What are the three complement pathways? Describe them simply

Answer 20

1. Classical (C1 recognises two IgG/IgM antibodies that have bound to a surface)
2. Alternative (C3b deposits on pathogen surface)
3. Lectin (Mannose binding lectin [MBL] attaches to mannose sugar on cell surface)

Question 21

How does complement initiate an inflammatory response

Answer 21

• Releases C3a, C4a, and C5a
• Binds to immune cells to trigger inflammatory response