The Immune System

Question 1

What is the immune system?

Answer 1

Our first line of defence against malicious invaders

Question 2

What does the immune system do when activated?

Answer 2

It triggers cells called leucocytes and macrophages and acute phase proteins that travel to the site of attack to identify, kill and remove invading pathogens

Question 3

What does the acute phase response do?

Answer 3

It generates symptoms like fever, aches and pains, sleepiness, loss of appetite and disinterest

Question 4

How does the acute phase response help us?

Answer 4

It helps to combat infection, conserve energy and aid repair

Question 5

How can acute phase response harm us?

Answer 5

When activated too much or for too long they can be very damaging

Question 6

What are responses to disease regulated primarily by?

Answer 6

Hypothalamus

Question 7

How does the brain control the immune system?

Answer 7

Brain receives signals from injured or infected tissues that may be neural or humoral

Question 8

Where are neural signals to the brain from?

Answer 8

C fibres and vagus nerve from the liver

Question 9

What does the liver do?

Answer 9

Produce acute phase proteins

Question 10

What is the nature of the main circulating signals to the brain?

Answer 10

Prostaglandins and complement proteins

Question 11

What is prostaglandins inhibited by?

Answer 11

Aspirin

Question 12

What are complement proteins?

Answer 12

A cascade of proteins important in killing invader cells

Question 13

What is the most important signals?

Answer 13

Cytokines

Question 14

What are cytokines?

Answer 14

Small proteins that are crucial in the growth and activity of other immune system cells and blood cells

Question 15

In what quantities are cytokines produced?

Answer 15

They are normally produced at very low levels but are switched on quickly in response to disease or injury

Question 16

What do cytokines include?

Answer 16

Interferons, interleukins, tumour necrosis factors and chemokines

Question 17

Where are cytokines produced and act?

Answer 17

Many are produced locally within damaged tissues and act on cells nearby but some enter the bloodstream where they send signals to distant organ including the brain

Question 18

What is the function of cytokines?

Answer 18

Chemically induced tissue repair and regulate immune reactions

Question 19

What triggers cytokine production?

Answer 19

Bacterial or viral products, damage to cells or threats to cell survival such as toxins or low levels of oxygen

Question 20

What is an important regulator of cytokine production?

Answer 20

Through neural signals to tissues can switch cytokines on or off

Question 21

Where do cytokines stimulate?

Answer 21

Most stimulate the immune system and the key components of inflammation such as swelling, local changes in blood flow and the release of a second wave of inflammatory molecules

Question 22

Where do cytokines act on?

Answer 22

They act on almost all physiological systems

Question 23

How are stress and the immune system linked?

Answer 23

Activation of the hypothalamic-pituitary-adrenal (HPA) axis

Question 24

How is the HPA axis activated?

Answer 24

Main responses to stress in the brain is increased production of a protein in the hypothalamus called corticotrophin releasing factors (CRF) which travels short distance from the hypothalamus to the pituitary gland to release another hormone, adrenocotrophin releasing factor (ACTH). This hormone travels via the circulation to the adrenal gland to release steroid hormones, cortisol in humans, which are some of the most powerful suppressors of immune function and inflammation

Question 25

What are active contributors to brain diseases such as multiple sclerosis, stroke and Alzheimer’s?

Answer 25

Defence molecules such as cytokines

Question 26

What is the impact of overproduction of cytokines?

Answer 26

It can damage neurons