Immune system - P2

Question 1

describe structure of human immunodeficiency virus (HIV)

Answer 1

capsid
reverse transcriptase
rna
lipid envelope made of host cell cell membrane
attachment proteins

Question 2

Describe the replication of HIV in helper T cells

Answer 2

1. HIV infects T helper cells (host cell) - HIV attachment protein attaches to a receptor on the helper T-cell membrane
2. Virus lipid envelope fuses with cell surface membrane and capsid released into cell which uncoats, releasing RNA and reverse transcriptase into cytoplasm
3. Viral DNA is made from viral RNA - Reverse transcriptase produces a complementary viral DNA strand from viral RNA template
   - Double stranded DNA is made from this (DNA polymerase)
4. Viral DNA integrated into host cell’s DNA (by enzyme integrase)
5. This remains latent for a long time in host cell until activated
6. Host cell enzymes used to make viral proteins from viral DNA (within human DNA) → viral proteins assembled with viral RNA to make a new virus
7. New virus bud from cell (taking some of cell surface membrane as envelope)
8. Eventually kills helper T cells
9. Most host cells are infected and process repeat

Question 3

Explain how HIV causes the symptoms of AIDS – acquired immune deficiency syndrome

Answer 3

• Infects and kills helper T cells (host cell) as it multiplies rapidly
• T helper cells then can’t stimulate cytotoxic T cells, B cells and phagocytes → impaired immune response
• Immune system deteriorates
• More susceptible to infections
• Diseases that wouldn’t cause serious problems in healthy immune system are deadly (opportunistic infections) e.g. pneumonia

Question 4

Explain why antibiotics are ineffective against viruses

Answer 4

• Antibiotics can’t enter human calls – but viruses exists in its host cell (they are acellular)
• Viruses don’t have own metabolic reactions e.g. ribosomes (use of the host cell’s) which antibiotics target
• If we did use them… act as a selection pressure + gene mutation = resistant strain of bacteria via natural selection → reducing effectiveness of antibiotics and waste money
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Question 5

why does not being able to produce immune response due to aids lead to death

Answer 5

infected by pathogen
pathogen reproduces in host cell
damages cell
releases toxins

Question 6

what is a monoclonal antibody

Answer 6

• Monoclonal antibody = antibody produced from a single group of genetically identical (clones) B cells / plasma cells

Question 7

describe use of monoclonal antibodies

Answer 7

• Monoclonal antibody = antibody produced from a single group of genetically identical (clones) B cells / plasma cells
• Identical structure
• Bind to specific complimentary antigen
• Have a binding site / variable region with a specific tertiary structure / shape
• Only one complementary antigen will fit

Question 8

why are monoclonal antibodies useful in medicine

Answer 8

• Only bind to specific target molecules / antigens because…
• Antibodies have a specific tertiary structure (binding site / variable region) that’s complementary to a specific antigen which can bind/fit to the antibody

Question 9

Explain how Monoclonal antibodies are used in targeting medication to specific cell types by attaching a therapeutic drug to an antibody e.g. in the treatment of cancer cells

Answer 9

1. Monoclonal antibodies made to be complementary to antigens specific to cancer cells → cancer cells are abnormal body cells with different antigens (tumour markers)
2. Anti-cancer drug attached to antibody
3. Antibody binds / attaches to cancer cells (forming antigen-antibody complex)
4. Delivers attached anti-cancer drug directly to specific cancer cells so drug accumulates → fewer side effects e.g. fewer normal body cells killed

Question 10

Explain the use of antibodies in the ELISA

Answer 10

• Can determine if a patient has
  a) Antibodies to a certain antigen
  b) Antigen to a certain antibody
• Used to diagnose diseases or allergies (e.g. HIV / Lactose intolerance)

Question 11

Explain why the use of controls when performing the ELISA test is necessary

Answer 11

• Controls enable a comparison with the test
• To show that:
• Only the enzyme and nothing else causes colour change
• Washing is effective and all unbound antibody is washed away

Question 12

ethical issues associated with the use of monoclonal antibodies

Answer 12

• Animals are involved in the production of monoclonal antibodies
• Although effective treatment for cancer and diabetes has caused deaths when used in treatment of Multiple Sclerosis
• Patients need to be informed of risk and benefits before treatment so they can make informed decisions