Innate Immunity 1

Question 1

What is innate immunity?

Answer 1

The first line of defence against infection. Present from birth and passed down through genes.

Question 2

What are the different types of innate barriers:

Answer 2

Physical (e.g. skin and GI tract)

Soluble (e.g. complement, defensins and collectins)

Induced (e.g. innate immune cells, pattern recognition receptors (PRRs) and interferon)

Question 3

What does complement do?

Answer 3

Enhances the ability of antibodies and phagocytic cells

Question 4

What are defensins?

Answer 4

Host defence peptides

Question 5

What are collectins?

Answer 5

Soluble pattern recognition receptors (PRRs)

Question 6

What is interferon?

Answer 6

Signalling proteins made and released by host cells in response to a presence of a virus

Question 7

What two types of factors get released when tissue damage occurs?

Answer 7

• Vasoactive (affects blood dilation)

- Chemotactic (causes cellular migration)

Question 8

How do vasoactive factors lead to the destruction of bacteria?

Answer 8

1) Lead to increased blood flow and permeability at capillaries
2) More exudate and cells can enter
3) Phagocytes migrate to the site of inflammation (chemotaxis)
4) Phagocytes and antibacterial exudate then destroy the bacteria

Question 9

How does complement work?

Answer 9

• Lyse bacteria
• Opsonise bacteria (mark them for phagocytosis)
• Induces inflammation

Question 10

What are lysozyme and where are they found and released?

Answer 10

Enzymes that disrupt bacterial cell walls.

Found in blood and tears
Released phagocytes and Paneth cells from the small intestine

Question 11

What do pentraxins, ficolins and collectins do?

Answer 11

Bind to pathogens and target them for phagocytosis and activate complement.

Question 12

What do antimicrobial peptides do?

Answer 12

Disrupt bacterial membranes

Question 13

How do lysozymes work?

Answer 13

Cleave the bonds between alternating sugars in peptidoglycan.

This makes them the most effective against gram-positive bacteria

Question 14

What are some examples of antimicrobial peptides?

Answer 14

Histatins (activate against pathogenic fungi such candidas albicans)

Cathelicidins (LL-37 broad spectrum antimicrobial activity against both gram-positive and gram-negative bacteria)

Defensins

Question 15

What are the two classes of defensins

Answer 15

alpha and beta

Question 16

Why are defensins amphipathic peptides?

Answer 16

Because they have hydrophilic and hydrophobic regions

Question 17

How do defensins disrupt the membranes of pathogens?

Answer 17

Form pores in the membrane

Question 18

How do collectins bind to pathogens and what do they bind to?

Answer 18

Cell-surface sugars with their lectin-like globular heads

Question 19

What do ficolins recognise?

Answer 19

Acylated compounds (COCH3), some of which are found in bacterial cell walls.

Question 20

What type of pathways are the classical, lectin and alternative pathways?

Answer 20

Complement pathways

Question 21

What do the complement pathways share in common?

Answer 21

All produce C3 convertase (C4b2a) within the pathway

Question 22

What are the complement pathways made up of and where are they found?

Answer 22

Made up of over 30 proteins and they are constantly circulating in the blood and fluids that bathe the cells

Question 23

How does the complement pathways lead to an amplification of a signal?

Answer 23

When it detects the presence of a foreign material, it initiates a cascade of reactions that amplify the signal.

Question 24

What is C1 made up of?

Answer 24

C1q (majority), C1r and C1s

Question 25

How is C1q arranged?

Answer 25

C1q has 18 polypeptides that form 6-collagen-like triple helix structures (stalk).

Question 26

How does C1 activate the classical pathway?

Answer 26

C1 binds to the Fc region of an antibody-antigen complex (but it must bind to another Fc region)