Immunity

Question 1

State 2 differences between a specific and a non-specific defence mechanism.

Answer 1

specific vs non-specific
1. specific pathogens vs all
2. slower vs rapid

Question 2

Among other places, lysosomes are found in tears.
Suggest a reason why this is so.

Answer 2

• protective covering of eye - thin to allow light through
• vulnerable to infection
• tear ducts = potential entry points for pathogens

Question 3

What are pathogens?

Answer 3

• disease causing microorganisms
• that trigger an immune response
  /
• viruses
• bacteria
• fungi
• protozoa

Question 4

What are antigens?

Answer 4

• generate immune response when detected by the body
• usually proteins
• on surface of cells

Question 5

What do antigens allow the immune system to identify?

Answer 5

1. pathogens
2. abnormal cells (cancerous cells/ tumours)
3. toxins (by bacteria)
4. foreign **cells from other organisms of same species **(eg. organ transplant)

Question 6

State 2 similarities between B cells and T cells.

Answer 6

1. form of wbc
2. produced from stem cells

Question 7

State 2 differences between T cells and B cells.

Answer 7

1. cell-mediated vs humoral immunity
2. mature in thymus gland vs bone marrow

Question 8

What is a macrophage?

Answer 8

• Phagocytic cell
• releases lytic enzymes
• break down pathogenic cells

Question 9

What do neutrophils do?

Answer 9

• engulf
• digest pathogens

Question 10

What do phagocytes do?

Answer 10

• engulf pathogens
• destroy them using lysosomes
• then become APCs

Question 11

Function of APCs

Answer 11

• present pathogenic antigens on cell mem
• signal T-lymphocytes

Question 12

What do T-helper cells do?

Answer 12

Stimulate:
1. cytotoxic T-cells–> divide & proliferate
2. B-cells–> divide
3. further phagocytosis
4. memory T-cells (immunological memory for future infection)

Question 13

What do cytotoxic T-cells do?

Answer 13

• kill infected cells
• through release of an enzyme that kills the cell

Question 14

What are vaccines?

Answer 14

• a way of introducing antigens of a
• dead/ weakened pathogen into the body
• to stimulate production of antibodies & memory cells

Question 15

State the 4 ways pathogens are made harmless to be used in vaccines.

Answer 15

1. killing 🔪but leaving antigens unaffected (eg. cholera)
2. weakening (attenuation)🫥- heating🔥 but leaving antigens (eg. oral vaccine against polio)
3. purified 😇antigens removed from pathogen (eg. hepatitis B)
4. inactivated toxins (toxoids)🤐- harmless but still triggers immune response (eg. Tentanus)

Question 16

Why do some vaccines contain multiple antigens?

Answer 16

• protects against diff. strains of pathogens (eg. flu)/ diff. diseases (eg. MMR)

Question 17

Why don’t vaccinations fully eliminate diseases?

Answer 17

1. x induce immunity in some ppl (immunodeficiency)
2. infected before enough antibodies for protection (slow primary response)
3. antigenic variability- mutations
4. objections to vaccinations ∵ moral, religious, ethical

Question 18

Compare active and passive immunity.

Answer 18

A vs P
- long term vs short term
- ✔️immune response (make antibodies) vs ❌
- ✔️memory cells vs ❌

Question 19

What are natural and artificial active immunity?

Answer 19

• natural- after being infected
• artificial- vaccination

Question 20

What is passive immunity?

Answer 20

• given antibodies
• made by diff. organism

Question 21

Give an example of natural passive immunity.

Answer 21

baby gets antibodies through:
1. placenta- maternal antibodies to foetal blood
2. colostrum- first breast milk

❗protection- temporart (only a few months after birth)- broken down in spleen & liver, x memory cells

Question 22

Cholera
1. what it is
2. why no effective vaccine
3. symptom
4. factors increasing spread

Answer 22

1. intestinal disease
2. intestinal = hard to reach by immune system
3. chronic diarrhoea
4. ↑ mutation rate- antigenic variability + mobile pop

Question 23

Cholera
1. what it is
2. why no effective vaccine
3. symptom
4. factors increasing spread

Answer 23

1. intestinal disease
2. intestinal = hard to reach by immune system
3. chronic diarrhoea
4. ↑ mutation rate- antigenic variability + mobile pop

Question 24

Tuberculosis
1. risk factor
2. factors increasing spread

Answer 24

1. ↑ HIV spread ↑ susceptible
2. overcrowding, poor living conditions in poverty/ war-affected countries + mobile pop + growing elderly pop ↓ effective immune system ↑ susceptibility

Question 25

Why is HIV called a retrovirus?

Answer 25

- reverse transcriptase converts RNA into DNA - **reverse of action of transcriptase**

Question 26

Briefly HIV vs AIDS

Answer 26

- HIV = **virus** - AIDS = **condition** caused by HIV infection

Question 27

Tuberculosis- spread through air Suggest why widespread use of condoms might help reduce the incidence of TB in a population.

Answer 27

- condoms- **prevents HIV infection** - ↓ no. of ppl w/ **impaired immune systems**- likely to **contract & spread** TB

Question 28

What are monoclonal antibodies?

Answer 28

- produced by **plasma cells** - all clones of **one B-cell**

Question 29

Why is detergent added to the mixture of B cells and tumour cells in developing hybridoma cells?

Answer 29

- affects **lipid** component in mem--> **holes** - detergent **washed out** --> **mem reform** - in **combination** w/ **adj cells**

Question 30

Explain why tumour cells are used to fuse with B-cells.

Answer 30

- **B cells- short-lived**, x divide outside body - **tumour cells**- long-lived, **divide outside body** - ==> **long-lived B cells grown outside of body**