Innate Immunity

Question 0

What is innate immunity?

Answer 0

Innate immunity is the generic, non specific response to infection. It does not confer lasting immunity. Immediate response against pathogens, eg inflammation.

Question 1

What are the seven parts of innate immunity?

Answer 1

Exclusion
Phagocytosis
Activation of complement 
Activation of interferons
Activation of nkcs 
Activation of mast cells 
Killing by eosinophils.

Question 2

How does the body exclude pathogens?

Answer 2

Through the skin which acts as a barrier. Through lowering the pH of the stomach and urine, though ciliated and non ciliated mucosa, produces mucous and microbial competition.

Question 3

How is skin barrier?

Answer 3

The skin is formed of a continually regenerative epidermis generating a tough impermeable layer of keratin.

1. Continue shedding of surface epithelial cells carries away potential pathogens.
2. Epidermal cells form a water resistant barrier that resist micro bacterial invasion.
3. Sebaceous glands secrete sebum which reduces skin pH and defending disrupt a bacterial membrane,
4. Harmless commensal bacteria have evolved to survive on the skin surface and outcompete pathogenic bacteria to inhibit growth.

Question 4

What occurs in phagocytosis?

Answer 4

Cells engulf pathogen to form an internal vehicle called a phagosome which then fuses with the pathogen and digests it in four main ways:

• generation of reactive oxygen species
• release of proteolytic enzymes
• reduction in pH
• cytokine synthesis.

Question 5

What are the main types of phagocytes?

Answer 5

Neutrophils and macrophages are the main phagocytes, they bind to pathogens via tlr. they have increased metabolic rate.

Question 6

What are the two main killing methods?

Answer 6

Oxygen dependent; highly reactive oxygen species created via a respiratory burst using ATP
Oxygen independent: rely of preformed toxic mediators in the lysosomes. Fuse to release in phagolysome.

Question 7

What are complements?

Answer 7

The complement system helps to clear pathogens. They are synthesised in the liver and circulate in the blood stream.
C3a and c5a. Activate phagocytes, attract inflammatory cells via chemotaxis, degranulate mast cells.
C3b: acts as an oposin.
C5b and c9: form the membrane complement attack complex to disrupt bacterial cell membranes causing cell death.

Question 8

What are Mhc molecules?

Answer 8

Mhc 1 are expressed by all cells. Mhc 2 used to present molecules to the immune system only in dendritic, macrophages and B cells.

Question 9

What are natural killer cells?

Answer 9

Check Mhc 1 and secret perforin if not recognised. Produce and secrete interferons.

Question 10

What are interferons?

Answer 10

Secreted by host cell and activate immune cells and up regulate antigen presentation.
Nkc release inf g when Lps is seen, it increases Mhc 1 expression,
Inf a and b are released by infected cells as a warning.

Question 11

What are mast cells?

Answer 11

Contain granules which are released upon activation and degranulation.
Granules contain preformed mediators like histamine and serotonin. And the mast cell also synthesises cytokines and protaglandins which cause vasodilation and platelet aggregation.

Question 12

What are the effects of histamine?

Answer 12

Increases blood flow and increases vasodilation.
Increases capillary perm
Pain through stimulation of nerve ends causing itch.

Question 13

How do eosinophils kill pathogens?

Answer 13

Mainly helminths. Kills via:
Respiratory burst releasing reactive oxygen species, release toxic and basic products and release lipid mediators to cause inflammation.