Immunity

Question 1

What is the first line of defence in the immune response?

Answer 1

Physical and chemical barriers:

• Skin and mucous membranes
• HCl from stomach

Question 2

What is the second line of defence in the immune response?

Answer 2

-Phagocytes
-Inflammation
This increases permeability of red blood cells in an area (swelling/pain etc.)

Question 3

What happens in phagocytosis?

Answer 3

• Foreign antigen
• Phagocyte recognises with chemoattrctants
• Engulfs pathogen through Endocytosis
• Lysosomes fuse with vacuole and release lysozymes
• Lytic enzymes hydrolyse pathogens
• Macrophage becomes ‘antigen presenting’
• Helper T cell sees this and releases proteins to activate other cells

Question 4

Where are helper T cells found?

Answer 4

T for thymus

Question 5

How do the Helper T cells trigger a macrophage response?

Answer 5

By releasing lymphokines

Question 6

What is the cell mediated response?

Answer 6

• Helper T cell releases interleukin
• Activates cytotoxic T cells
• produces memory cells that recognise antigens to provide a secondary immune response
• produces effector T cells that release perforins to kill cancer and virus cells

Question 7

What are perforins?

Answer 7

Proteins that cause cells to burst, empties contents

Question 8

What activates the humoral response?

Answer 8

Helper T cells release cytokines

Question 9

What is the initial humoral response?

Answer 9

• B cell recognises antigen

- Antigen- receptor complex, which triggers Helper T cell activation of B cell replication

Question 10

Replication of B cells

Answer 10

Plasma cells
- secrete antibodies
- each B cell only makes one type of antibody
Memory cells
- recognise past antigens to provide a secondary immune response

Question 11

Where a B cells found?

Answer 11

Found in bone marrow

Question 12

Why do common colds effect people even once they’ve had it?

Answer 12

This is due to antigen variability, due to gene mutations and natural selection, the antigen changes shape so that the body can no longer recognise it.

Question 13

Why don’t we normally get the same infection twice?

Answer 13

Both B cells and cytotoxic T cells produce memory cells that will remember how to fight the antigen. When an antigen is recognised, the memory cells will be activated to produce plasma cells that can create specific antibodies.

Question 14

How is HIV spread?

Answer 14

Through the exchange of body fluids

Question 15

How does HIV cause disease?

Answer 15

• HIV GP120 receptor attaches to surface of Helper T cell (CD4 receptor)
• viral reverse transcriptase enzyme makes DNA copy of viral RNA
• Virus DNA is inserted into DNA of T cell, viral DNA stays inactive for a while
• Virus becomes ‘active’ and helper T cell makes new viruses
• New viruses released from cell, infecting and killing other helper T cells.
• Destruction of T cells result in AIDs

Question 16

What are monoclonal antibodies?

Answer 16

identical copies of antibodies made in laboratories, and that come from one plasma cell. They have been isolated and cloned

Question 17

How are monoclonal antibodies produced?

Answer 17

• Injecting particular antigens into an animal like mice
• Mice produce plasma cells with antibodies
• Tumour cells added to plasma cells to create hybridomas

Question 18

What are hybridomas?

Answer 18

A fusion of tumour cells and plasma cells that can rapidly produce antibodies

Question 19

What ethical issues surround the use of monoclonal antibodies?

Answer 19

• It requires giving cancer to mice
• You need to make animals transgenic
• Testing on humans has resulted in organ failure
• Some Multiple Sclerosis patients have died as a result

Question 20

What is the use of monoclonal antibodies in pregnancy testing?

Answer 20

• Women produce hCG in urine when pregnant
• Home pregnancy tests contain monoclonal antibodies that form a coloured complex when hCG
• Makes a coloured line appear on a positive pregnancy test

Question 21

What does hCG stand for?

Answer 21

Human chronic gonadatrophin

Question 22

Describe the procedure of the ELISA test

Answer 22

• Apply blood sample to a slide where the antigens can attach
• Wash surface to remove unattached antibodies
• Add complementary monoclonal antibodies to attach to the antigens
• Wash again to remove excess antibodies
• Add second antibody complementary to first and has an enzyme attached.
• Add the colourless substrate of the enzyme, when hydrolysed produces a coloured substance
• Concentration of antigen is relative to colour intensity

Question 23

What are the uses of the ELISA test?

Answer 23

• To detect HIV and pathogens of other diseases such as TB and hepatitis B
• Useful to measure quantities of antigens in blood

Question 24

How are the products of phagocytosis removed?

Answer 24

Soluble debris is removed by exocytosis and harmless products are absorbed

Question 25

How do vaccines lead to the production of a specific antibody

Answer 25

1. Vaccine contains antigen
2. Phagocytes engulf and become antigen-presenting
3. Stimulates specific helper T cell which releases cytokines to stimulate specific B cell
4. B cell divides
5. Plasma cell produces antibody