L2- Innate Immunity

Question 1

What are examples of 1st line barriers to entry in the innate immune system?

Answer 1

SKIN- antibacterial, antiseptic protective layer

RESPIRATORY TRACT- tight cell junctions, cilia, mucus

GI TRACT- peristalsis, acidic pH

TEARS, SWEAT, SALIVA- lysozymes destroy bacterial cell walls

MICROBIAL COMPETITION- bacteria that normally live in the body can prevent the pathogen from growing

Question 2

What are cytokines?

Answer 2

Intercellular messenger proteins produced by many cells in the body controlling immune defences.

They bind to specific receptors to activate/deactivate immune responses.

Question 3

What are examples of cytokines?

Answer 3

IL1, 1L6- fever, inflammation

IL12- Th differentiation

TNF alpha- fever, macrophage activation

Question 4

What are chemokines?

Answer 4

Class of cytokines with chemoattractant properties.

Promote inflammation by enabling adherence of cells to blood vessel surfaces and migration to infected tissues

e.g IL8,MCP

Question 5

What are interferons?

Answer 5

Produced in response to virally infected cells

e.g IFN alpha, IFN beta, IFN gamma

Question 6

What does IFN gamma do?

Answer 6

Produced by NK cells
Stimulates macrophages
Stimulates Th differentiation

Question 7

What are examples of second line of defence in the innate immune system?

Answer 7

Secreted compounds such as cytokines, natural antibodies, complement

Cellular components such as phagocytes and natural killer cells

Question 8

How does the innate immune system recognise pathogens?

Answer 8

Pathogen associated molecular patterns found on pathogens are recognised by pattern recognition receptors on innate immune cells.

Question 9

What are the main classes of PRRs?

Answer 9

Toll Like Receptors (important in fungal infections)

Collectins

Question 10

What are the different TLR’s and their ligands?

Answer 10

TLR-4= LPS (-,+)
TLR-5= Flagellin
TLR-7= RNA (viruses)

Question 11

What is the mechanism of phagocytosis?

Answer 11

1. Recognition of pathogen by receptors on phagocyte.
2. Chemotaxis and adherence of microbe to phagocyte.
3. Ingestion of microbe.
4. Formation of phagosome.
5. Digestion of microbe by enzymes by fusion of phagosome with lysosome to form phagolysosome.
6. Digestion of microbe.
7. Formation of residual body containing indigestible material.
8. Discharge of waste.

Question 12

What are alternative killing mechanisms of neutrophils?

Answer 12

Reactive O2 intermediates-
O2 uptake after phagocytosis (resp burst)
O2 reduction by NADPH forms radicals
Oxygen radicals form which cause DNA damage and alterations to bacterial membranes
Neutralised to water and oxygen by catalase

Question 13

What are alternative killing mechanisms of macrophages?

Answer 13

L-arginine conversion to L-citrulline produces NO radicals.

Radicals cause DNA damage and bacterial membrane alterations.