Immune System Overview

Question 1

What’s the first line of defence of the immune system?

Answer 1

Innate immune system (nonspecific)
External barricades: skin, muscous membranes
Internal defences: phagocytes, antimicrobial proteins, attack cells
Chemical defenses

Question 2

What is the second line of defence of the immune system?

Answer 2

Adaptive immune system (specific/acquired)

Question 3

What is skin?

Answer 3

An organ of tough keratinised epithelial membrane

Question 4

What are mucous membranes?

Answer 4

Line any cavity that opens up to the outside world; respiratory, digestive, urinary, reproductive tract

Question 5

List 5 chemical defenses of the innate immune system

Answer 5

1. Acid from skin, stomach, and vaginal secretions
2. Mucin that forms mucus in the respiratory and digestive passageways
3. Enzymes found in saliva, mucus, and eye fluid that fight bacteria
4. Defensins, or antimicrobial proteins
5. Chemicals found in sweat that destroy bacteria

Question 6

3 internal innate defenses

Answer 6

1. Fever
2. Chemical signals
3. Inflammation

Question 7

The order of arrival of defensive cells

Answer 7

1. Phagocytes (neutrophils and macrophages)
2. Natural Killer (NK) cells

Question 8

Neutrophils

Answer 8

Most abundant type of white blood cell
Self-destruct after ingesting a pathogen
Dead neutrophils = pus

Question 9

Macrophages

Answer 9

Made of monocyte white blood cells that have moved out of the blood stream to occupy tissues
Free type - patrol tissues
Fixed type - attached to fibres in specific organs (ie the Stellate macrophages in the liver)
Attaches to bacterium using cytoplasmic extensions, brings it closer and engulfs it, digesting it, and displays particles on its surface

Question 10

Natural Killer cells

Answer 10

Patrol blood and lymph looking for abnormal cells
Unique - can kill your own cells if they are infected with viruses or have become cancerous (know because the cell won’t contain MHC1). It then gives the cell an enzyme that triggers apoptosis

Question 11

What is MHC1?

Answer 11

Major Histocompatibility Complex 1
Normal healthy cells contain this protein on their surface - pieces of endogenous proteins (proteins made within that cell)
If a cell is infected, it stops making this protein

Question 12

Strategy of the Immune Response

Answer 12

1. Inflammatory repsonse

Question 13

What are symptoms of the inflammatory response?

Answer 13

Redness
Swelling (due to increased blood vessel permeability)
Heat (increases the cell’s metabolic rate)
Pain

Question 14

What is histamine and what releases it?

Answer 14

Mast cells in connective tissue release histamine
Causes vasodilation
Causes increased permeability of blood vessels - causes nearby capillaries to release protein rich fluids (helps clot blood and build scabs, lymphatic system filters extra fluid, also allows phagocytes to enter inflamed area, and lymphocytes)

Question 15

What are chemical signalling molecules of the inflammatory response?

Answer 15

Histamine (released by mast cells in connective tissue)
Fatty acid prostoglandins
Kininogen and other plasma proteins
Complement blood proteins
Cytokines

Question 16

What are lymphoytes?

Answer 16

Destroy pathogens
Clean up dead cell wreckage

Question 17

Leukocytosis

Answer 17

The release of neutrophils from bone marrow (where they’re made) into the blood stream
Inflamed endothelial cells and capillaries send out chemicals to attract neutrophils
Neutrophils stick to the capillary walls and squeeze through epithelial cells

Question 18

Monocytes

Answer 18

Arrive at the site of injury and transfrom into macrophages

Question 19

What are pyrogens?

Answer 19

Chemicals released by immune cells (neutrophils, macrophages, lymhocytes) that travel to the hypothalamus and raise body temperature (systemic fever)
Fever causes increased cell metabolism, and cause liver and spleen to hold on to all iron and zinc so it can’t contribute to bacterial growth

Question 20

Two types of growth of the adaptive immune system

Answer 20

Organic - touching germs on a doorhandle
Premeditated - vaccines

Question 21

What are the key differences between the adaptive and the innate immune system?

Answer 21

1. Adaptive has the ability to remember specific pathogens
2. Adaptive is systemic (innate is more local)
3. Adaptive is specific

Question 22

What are the 2 defenses of the adaptive immune system?

Answer 22

1. Humoral immunity
2. Cellular defenses

Question 23

What is your humoral immunity?

Answer 23

Production of antibodies
Made by specialised white blood cells and patrol the body’s humors (fluids - ie blood and lymph)

Question 24

B Lymphocyte

Answer 24

Originates and matures in bone marrow
Maturing allows it to distinguish self from non-self
Develops immunocompetence and self-tolerance
When mature, displays at least 10,000 special protein receptors on surface (membrane-bound antibodies)
Each B lymphocyte has specific antibodies
Mature B lymphocytes then roam around in secondary lymphoid organs

Question 25

What is immunocompetence?

Answer 25

How to recognise and bind to a particular antigen

Question 26

List the secondary lymphoid organs?

Answer 26

Spleen, tonsils, lymph nodes

Question 27

What happens when a B lymphocyte binds to a pathogen it has an antibody for?

Answer 27

Upon binding the pathogen the cell becomes activated, and quickly starts multiplying Most activated cells become effector (plasma) cells Some become memory cells (allows for secondary immune response)

Question 28

How do effector (plasma) cells work?

Answer 28

Have extra ER Mass produce the antibodies and release them into the humor at roughly 2000 antibodies per second for 4/5 days until the cells die

Question 29

What is opsonisation?

Answer 29

Free floating antibodies bind to antigens on pathogens and mark the cells for death

Question 30

What is neutralisation?

Answer 30

Antibodies bind to all available antigens on a pathogen, thereby blocking the pathogen from attaching to tissues

Question 31

What is agglutination?

Answer 31

Antibodies have more than one binding site, and can therefore bind to more than one antigen to form clumps which make it easier for macrophages to locate and ingest them

Question 32

Another function of antibodies

Answer 32

Antibodies call in phagocytes from the innate immune system and special lymphocytes from the adaptive system to destroy the antigen-antibody clumps

Question 33

Active humoral immunity

Answer 33

B cells bump into antigens and produce antibodies (can occur natrually or artificially)

Question 34

Passive humoral immunity

Answer 34

Infants get passive humoral immunity (antibodies) from their mother through the placenta and breast milk Passive antibodies however, don't live long, and don't produce effector or memory cells Can also acquire passive immunity by getting exogenous antibodies from the plasma of an immune donor (not the same as a vaccine, but can buy the patient some time)

Question 35

Cellular Immune Response

Answer 35

T lympocytes go after infected host cells

Question 36

What are the functions of T cells?

Answer 36

Causes inflammation Activates macrophages Recruits other T cells Regulate much of the immune response

Question 37

What are Major Histocompatibility Complexes (class II)?

Answer 37

Bits of a pathogen that the cell has broken down can bind to MHC molecules and are now displayed on its surface Done by both innate and adaptive immune cells

Question 38

What are Professional Antigen Presenting Cells?

Answer 38

Cells of the innate and adaptive immune system that present broken pieces of the pathogens that they've ingested

Question 39

Which cells are APC?

Answer 39

Macrophages, dendritic cells and B cells

Question 40

Where are T cells made and where do they mature?

Answer 40

Made: bone marrow Mature: thymus (lymphoid gland on top of the heart)

Question 41

Helper T cells

Answer 41

Naive helper T cell has a receptor specific for an MHC class II protein + a specific antigen on an APC If this matched, the two cells bind and the helper T cell is activated T cell divides producing mostly other helper T cells, but also regulatory T cells and memory T cells T cells release cytokines that when entering other T cells give them the signal to start dividing > some also help activate cytotoxic T cells

Question 42

Cytotoxic T cells

Answer 42

If cytotoxic T cells meet the correct specific MHC class II + antigen combination they bind Release perforins (create pores in the cell) and granzymes (a protease) which leads to apoptosis

Question 43

Immunodeficiencies

Answer 43

AIDS (acquired immudeficiency syndrome) caused by HIV (human immunodeficiency virus) attacks helper T cells

Question 44

Interaction between B and T cells

Answer 44

When a B cell has engulfed a protein and presented the antigen on its surface, a helper T cell checks if this is indeed a foreign body If yes, the helper T cell binds and releases cytokines which fully activate the B cell If not, nothing happens and no immune response is generated

Question 45

Regulatory T cells

Answer 45

At the end of infection, release inhibitory cytokines that tell other immune cells to stand down A type of effector cell

Question 46

Autoimmune disorders

Answer 46

Multiple sclerosis - eats away at the myelin sheaths around neurons Type 1 diabetes - destroys pancreatic cells that make insulin