The Immune System Flashcards
What is the immune system?
Our first line of defence against malicious invaders
What does the immune system do when activated?
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
What does the acute phase response do?
It generates symptoms like fever, aches and pains, sleepiness, loss of appetite and disinterest
How does the acute phase response help us?
It helps to combat infection, conserve energy and aid repair
How can acute phase response harm us?
When activated too much or for too long they can be very damaging
What are responses to disease regulated primarily by?
Hypothalamus
How does the brain control the immune system?
Brain receives signals from injured or infected tissues that may be neural or humoral
Where are neural signals to the brain from?
C fibres and vagus nerve from the liver
What does the liver do?
Produce acute phase proteins
What is the nature of the main circulating signals to the brain?
Prostaglandins and complement proteins
What is prostaglandins inhibited by?
Aspirin
What are complement proteins?
A cascade of proteins important in killing invader cells
What is the most important signals?
Cytokines
What are cytokines?
Small proteins that are crucial in the growth and activity of other immune system cells and blood cells
In what quantities are cytokines produced?
They are normally produced at very low levels but are switched on quickly in response to disease or injury
What do cytokines include?
Interferons, interleukins, tumour necrosis factors and chemokines
Where are cytokines produced and act?
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
What is the function of cytokines?
Chemically induced tissue repair and regulate immune reactions
What triggers cytokine production?
Bacterial or viral products, damage to cells or threats to cell survival such as toxins or low levels of oxygen
What is an important regulator of cytokine production?
Through neural signals to tissues can switch cytokines on or off
Where do cytokines stimulate?
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
Where do cytokines act on?
They act on almost all physiological systems
How are stress and the immune system linked?
Activation of the hypothalamic-pituitary-adrenal (HPA) axis
How is the HPA axis activated?
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
What are active contributors to brain diseases such as multiple sclerosis, stroke and Alzheimer’s?
Defence molecules such as cytokines
What is the impact of overproduction of cytokines?
It can damage neurons
