Disease and immunity

Question 1

What are the four main types of pathogen?

Answer 1

Bacteria
Viruses
Fungi
Protoctista

Question 2

What is active immunity?

Answer 2

Something that stimulates the production of antibodies and memory cells. Long-lasting.

Question 3

What is passive immunity?

Answer 3

Something that introduces antibodies from a outside source, but does not stimulate memory cell production. Short lived.

Question 4

What do natural and artificial mean in terms of active immunity?

Answer 4

Natural = From a body's own response
Artificial = Stimulating a response by introducing a dead or altered pathogen

Question 5

What do vaccines involve?

Answer 5

Introducing a modified antigen, killed pathogen or non-virulent pathogen to a person’s immune system

Question 6

What must good vaccines be?

Answer 6

Good vaccines must be:
· thoroughly tested to ensure few, if any, side effects
· economical to vaccinate a whole population or age group (routine)
· easy to produce, store, transport and administer

Question 7

What are some direct forms of transmission?

Answer 7

Physical contact
Droplet spread
Spores

Question 8

What are some indirect forms of transmission?

Answer 8

Airborne particles
Contaminated objects
Vectors
Contaminated food and water

Question 9

What factors can contribute to the spread of disease?

Answer 9

· hot, humid climate
· overcrowding and homelessness
· poor ventilation
· malnourishment and polluted water and food
· poor health and access to health care
· lack of hygiene and poor hygienic services

Question 10

Where can we get medicines from?

Answer 10

Medicines are from many microorganisms and plants; These can be antigens they produce, or even toxins.

Question 11

What key features do antibodies have?

Answer 11

· two binding sites
· variable regions that are complementary to different antigens
· constant region
· four polypeptide chains called immunoglobins

Question 12

What defences do plants have against invading pathogens?

Answer 12

Structural Chemical

Permanent Bark, waxy cuticle Not applicable
tough cell walls

Synthesised Callose deposition Cell suicide, toxic
substances,
pathogen-degrading
enzymes

Question 13

Why must you be careful with antibiotics, and how can you minimise this risk?

Answer 13

There may be some resistant bacteria which will then reproduce, forming an antibiotic resistant population. You can minimise this by rotating antibiotics often and only using them if completely necessary.

Question 14

What makes up the first line of defence against pathogens in animals?

Answer 14

· keratinised dead skin cells 
· blood clotting and wound repair 
· mucous membranes and cilia 
· inflammation 
· expulsive reflexes (diarrhoea and vomit)

Question 15

What do T helper cells do?

Answer 15

Recognise antigens displayed on phagocytes and stimulate specific T killer cells and B cells (clonal selection) to divide by mitosis (clonal expansion)

Question 16

What do T killer cells do?

Answer 16

These are cytotoxic – they kill infected cells by creating a hole in their cell membrane

Question 17

What do T memory cells do?

Answer 17

Remain in the blood to provide a rapid response to reinfection

Question 18

What do T regulator cells do?

Answer 18

Suppresses self-recognising immune cells

Question 19

What do B plasma cells do?

Answer 19

Release monoclonal antibodies which form an antigen–antibody complex, causing agglutination and attracting phagocytes to destroy the immobilised pathogens

Question 20

What do B memory cells do?

Answer 20

Remain in the blood to provide a rapid response to reinfection

Question 21

What do phagocytes produce and what do each of them do?

Answer 21

cytokines (regulate the immune response)
interleukines (trigger replication of other white blood cells)
opsonins (bind to a pathogen and signal for phagocytosis)
anti-toxins (bind and disable toxins)

Question 22

What are the stages of phagocytosis?

Answer 22

1. Pathogens produce chemicals that attract phagocytes
   
   2. Phagocytes recognise non-human proteins on the pathogen. This is general, non-self-reaction
   3. The phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome
   4. The phagosome combines with a lysosome to form a phagolysosome
   5. Enzymes from the lysosome digest and destroy the pathogen.

Question 23

What are the three modes of action of antibodies?

Answer 23

1. Opsonins - Coat pathogen binding sites so unable to infect cells. Phagocytes recognise the antibodies and
   engulf the pathogen.
2. Agglutination - Large antibodies bind many pathogens so clump is too large to enter cells and is more likely to be phagocytosed.
3. Anti-toxin precipitation - Soluble toxins released by bacteria are precipitated out of solution so can be phagocytosed more easily.

Question 24

Where does the cell-mediated response occur?

Answer 24

In the tissues

Question 25

Where does the humoral response occur?

Answer 25

In the bodily fluids / surfaces

Question 26

What are the stages of cell mediated response?

Answer 26

1. Phagocytes present antigens they have found
2. T helper cells fit the specific antigen. This causes them to produce interleukins which stimulate more T cells to divide by mitosis.
3. These cells can do any of the T cell functions.

Question 27

What are the stages of humoral response?

Answer 27

1. Activated T helper cells bind to the B cell APCs (antigen presenting cells). This cell then repeatedly divides.
2. Interleukins produced by activated T cells cause the B cells to activate.
3. These B cells divide by mitosis to form Plasma cells and B memory cells
4. These B cells produce antigens that combat the pathogen
5. The B memory cells stay in case of re-invasion