Immunology- An introduction to the immune system

Question 1

The immune system is a network of specialised cells, tissues and soluble factors that co-operate to kill and eliminate what?

Answer 1

Infections and diseases

Question 2

How does the immune system fight infections and diseases?

Answer 2

• By distinguishing ‘self’ molecules from ‘non-self’ molecules
• By identifying ‘danger’ signals (e.g from acute inflammation) or via combination of the two

Question 3

What are immune-suppresive and anti-inflammatory drugs essential for?

Answer 3

• Essential for thetreatment of autoimmune diseases, allergic diseases, asthma and cancer
• Key to preventing the rejection of donor tissues in transplant recipients

Question 4

What are the two types of immunity?

Answer 4

Innate

Adaptive

Question 5

What is innate immunity

Answer 5

Is present from continuously, it is a defense mechanism that is present from birth and is generally non-specific 9i.e the same generic response occurs towards many different types of material)

• First line of defence
• No memory

Question 6

What is adaptive immunity?

Answer 6

Is induced by the presence of ‘foreign’ or ‘non-self’ material. the response that occurs is usually unique to the specific substance or pathogen that induced the response

Question 7

What do both innate and adaptive immunity work closely together to do?

Answer 7

To eliminate disease-causing micro-organisms

Question 8

What are the points of entry for innate immunity?

Answer 8

• Digestive system
• Respiratory system
• Urogenital system
• Skin damage

Question 9

What are the routes of attack for the innate immunity?

Answer 9

• Circulatory system

- Lymphatic system

Question 10

For innate immunity what are the protective physical and chemical mechanisms?

Answer 10

• Outer surface which is tough and impermeable to micro-organisms
• Inner surface bathed in moving mucous and acid secretions
• Commensal organisms
• Anti-microbial peptides

Question 11

Specialised cells and molecules of innate immune response. How do phagocytic cells do this?

Answer 11

• Orchestrate initiation of response

- Recognise, ingest and kill bacteria and yeasts

Question 12

Specialised cells and molecules of innate immune response. How do degranulating cells do this?

Answer 12

• Orchestrate initiation of response

- Damage and kill multicellular parasites and viruses

Question 13

Specialised cells and molecules of innate immune response. How do secreted proteins do this?

Answer 13

• Complement (induced)
• Chemokines
• Cytokines

Question 14

What happens in the first stage of infection?

Answer 14

Physical (natural) barriers breached, pathogens invade, innate immune responses initiated

Question 15

What happens in the second stage of infection?

Answer 15

Tissue-resident innate immune cells recognise pathogens as ‘non-self’ and dangerous

Question 16

What happens in the third stage of infection?

Answer 16

Macrophages ingest invading extracellular bacteria

Question 17

What happens in the fourth stage of infection?

Answer 17

Mast cells step in and degranulation occurs where there is a release of pre-formed pro-inflammatory substances (e.g histamine)
Then gene expression occurs where there is a production of new pro-inflammatory substances

Question 18

What are some examples of pro-inflammatory mediators?

Answer 18

Nitric oxide

• Prostaglandins
• Histamines
• Pro-inflammatory cytokines

Question 19

In the 5th step of infection it is described at late innate response and acute inflammation occurs? How does this happen?

note- Its a positive feedback pathway

Answer 19

• Bacteria trigger macrophages to release cytokines and chemokines
• Vasodilation and increased vascular permeability cause redness, heat and swelling
• Inflammatory cells migrate into tissue, releasing inflammatory mediators that cause pain

Question 20

What does the term oponisation mean?

Answer 20

The coating of pathogens by humoral (soluble) factors

Question 21

What is C3a?

Answer 21

It is an anaphylatoxin which promotes acute inflammatory reactions

Question 22

What does inflammation promote?

Answer 22

• Vascular changes
• Recruitment and activation of neutrophils (trans endothelial migration)
• Bacteria produce chemicals that attract neutrophils to site of infection

Question 23

The process of trans endothelial migration can be divided up into a number of broad steps. What re these steps?

Answer 23

Weak binding ‘rolling’
Strong binding
Stable adhesion and aggregation
Transendothelial migration

Question 24

What does the neutrophil killing mechanisms induce?

Answer 24

Phagocytosis
Degranulation
NETs

Question 25

What is NETs?

Answer 25

Activated neutrophils release intracellular structure (NETs) into the extracellular environment
NETs serve to immobilise pathogens:
-Prevcents them from spreading
-Facilitates their phagocytosis

Question 26

For intracellular pathogens i.e viruses, virally infected cells produce and release cytokines called what?

Answer 26

Interferons

Question 27

What can Natural-Killer (NK) cells do?

Answer 27

Recognise and destroy virally-infected cells (and cancer cells)
They ignore normal healthy tissues and cells

Question 28

How long does innate immunity intermediate take to act?

Answer 28

0-4 hours

Question 29

How long does early induced innate response take to act?

Answer 29

4-96 hours