5. Cell Recognition and immune system

Question 1

How does the body detect pathogens?

Answer 1

Body can recognise ‘non self’ protiens on the set face of the cell

Question 2

What is an antigen

Answer 2

(Macromolecule) markers that allow cell to cell recognition. Can either be self or non self

Question 3

How do pathogens avoid causing a specific immune response?

Answer 3

Antigen variability, antigen change due to genetic mutations.
Memory cells can no longer bind

Question 4

How does passive immunity happen?

Answer 4

Anti-venoms, fetal immunity (breast milk)

No memory cells are made, immunity is temporary

Question 5

What is (natural) active immunity?

Answer 5

Organism is infected, triggering numeral immune response

Antibodies made but symptoms of disease may be displayed

Question 6

What is (artificial) active immunity?

Answer 6

Vaccination, body produces antibodies and memory cells providing long-term immunity

Without experiencing symptoms

Question 7

Describe process of phagocytosis

Answer 7

• phagocyte is attracted to pathogen by the pathogens chemical products
• pathogen attaches to receptors on phagocyte
• lysosomes migrate to forming phagosome as pathogen gets engulfed
• lysosomes release lysoZYmes into phagosome, these hydrolyse the pathogen
• pathogen absorbs hydrolysis products

[ext] phagocyte ‘present’ pathogens antigens. (Not part of cell phagocytosis)

Question 8

What are the two types of phagocytes?

Answer 8

Neutrophils
Macrophages

Question 9

Two examples of specific immune responses?

Answer 9

Cell mediated- T cells
(matured in thymus)

Humeral- B cells
(matured in bone marrow)

Question 10

Summarise the role of T cells in CELL-MEDIATED immunity

Answer 10

• receptors helper T-cell fit onto antigen presenting cell
• T-cell is activated to divide by mitosis
• cloned T cells can either:
  Become memory cell
  Stimulate phagocytosis
  Stimulate B cell
  Activate TC cell

Question 11

What is a TC cell?
Explain how they carry out function.

Answer 11

Cells that kill infected body cells by releasing the protein perforin. This protein makes holes in membrane

Question 12

When are b cell produced produced?

Answer 12

At birth, around 10 million of each are present in body.

B cells are not produced in response to pathogen, they only multiply in response to pathogen

Question 13

When b cells are cloned they can either be…

Answer 13

plasma cells or memory cell.

Question 14

What cells are involved in primary and secondary responses

Answer 14

Primary - PRODUCTION of antibodies and memory cells

Secondary - memory cells recognise pathogen, providing faster response on later infection

Question 15

How are monoclonal antibodies used to treat cancer? (indirect and direct)

Answer 15

DIRECT
Antibodies specific to cancer antigen blocks chemicals that stimulate uncontrolled growth.

INDIRECT
Radioactive or cytotoxic material is attached to MA, binding to and killing cancer

Question 16

How are monoclonal antibodies used in diagnosis

Answer 16

Eg. Prostate cancer causes an increase in PSA antibodies, this is detected and causes concern for further testing

The ELISA test

Question 17

Give three reasons why monoclonal antibodies raise ethical issues

Answer 17

Mice involved in production

Deaths linked with MA

drug testing (2006 six volunteers had multiple organ failure)

Question 18

What 5 things are necessary for an effective vaccination program

Answer 18

Economically viable

Few side effects

Viable transport, storage + production

Training of staff to perform vaccination

Majority of population must be vaccinated = herd immunity

Question 19

6 reasons why vaccination might not work

Answer 19

-will not work on people with defected immune systems

• disease may develop immediately after vaccination, potentially spreading to others

-antigen variability
-variants of the same pathogen

-Some pathogens ‘hide’ in body cells eg HIV

-some may object because of medical or ethical issues

Question 20

Discuss ethical issues of vaccination

Answer 20

Testing often involves animals

Potentially long lasting side effects

Risks involved in human testing

Should it be compulsory so herd immunity can be achieved?

Question 21

What do Plasma cells do?

Answer 21

Secrete antibodies into blood plasma. Survive for short amount of time but produce a lot of antibodies

Question 22

What do memory cells do?

Answer 22

Memory cells live longer, when they ‘recognise’ the same pathogen they divide rapidly and develop into plasma cells.
They provide readiness for future infections

Question 23

Summarize the humoral response.

Answer 23

B-cell takes up antigens of pathogens and presents them.

Helper T cells attach, activating B cell.

Stimulated to clone into plasma or memory cells.

Question 24

Draw and label an antibody

Answer 24

go online for images;
- light chain
- heavy chain
- constant region
- variable region
- antigen binding sites

Question 25

Explain how antigens are destroyed by antibodies.

Answer 25

• agglutination of bacterial cells, clumps of cells are formed (antigens have multiple binding sites) Easier for phagocytes to find.
• act as markers for phagocytes to engulf cells they are attached

Question 26

Where do T and B cells mature?

Answer 26

T cells, mature in thymus

B cells, mature in bone marrow

Question 27

Explain how vaccinations work.

Answer 27

• Small amounts of weakened/ dead pathogen injected
• B cells are activated (plasma/memory)
• memory cells remain in the bloodstream

Question 28

Explain the concept of herd immunity

Answer 28

If enough of the population is vaccinated, pathogens cannot easily spread.

protects those who aren’t vaccinated/ can’t get vaccinated.

Question 29

Draw the structure of HIV.

Answer 29

• RNA
• Reverse transcriptase
• capsid
• matrix
• attachment proteins
• membrane

Question 30

Summarize the replication of HIV

Answer 30

HIV is transported in blood until it attaches to a CD4 PROTEIN on a helper T-cell

HIV capsule fuses with the Th-cell, RNA and reverse transcriptase enter.

Th-cell synthesises new viral enzymes and RNA

Question 31

How do new viral RNA and proteins exit host cell? (HIV)

Answer 31

Move to cell membrane, and is released, New HIV molecules membrane is from Th-cell

Question 32

What is AIDS?

Answer 32

Replication of viruses via Th-cells interferes with immune response. The host is vulnerable to infections and cancer.

Question 33

Explain the process of the Enzyme linked immunosorbent assay (ELISA)

7 steps…

Answer 33

• add a test sample to the base of a beaker
• wash to remove any unbound test sample
• add an antibody, complementary in shape of antigen that is being tested for
• wash any unbound antibody
• add a second antibody antibody that is complementary to the first, enzyme attached to it, rinse unbound antibodies
• add substrate for enzyme - colorless in absence of enzyme, coloured in the presence of enzyme
• colour indicates presence of enzyme and therefore antigen. intensity indicates quantity present

Question 34

Why are antibodies ineffective against viruses?

Answer 34

viruses rely on host cells for metabolic pathways. no mechanisms for antibodies to disrupt.
inside organisms own cells, cant be reached