Cell Recognition And The Immune System (3.2.4) (B)

Question 1

What is vaccination?

Answer 1

• The process of injecting antigens into an individual to provide immunity

Question 2

How does vaccination work?

Answer 2

• Vaccines contain antigens from a specific pathogen that are dead or weakened
• Vaccines stimulate an immune response, including the production of plasma cells, which release specific antibodies and memory cells
• These memory cells provide long term immunity
• A booster dose can be given to encourage faster and greater antibody production if the pathogen is encountered again

Question 2

What is active immunity?

Answer 2

• When an individual is exposed to the antigen, produces antibodies and memory cells
• Takes time to develop but provides permanent immunity

Question 3

What is herd immunity?

Answer 3

• When a large proportion of the population is immune to a disease, then the spread of that pathogen is reduced

Question 4

Why is herd immunity important?

Answer 4

• This protects individuals who are not immune, such as those who cannot be vaccinated or have weakened immune systems, because the likelihood of encountering an infected person is reduced

Question 5

What is passive immunity?

Answer 5

• When an individual receives pre-formed antibodies from another source
• Is immediate but provides temporary immunity

Question 6

What is HIV?

Answer 6

• Human immunodeficiency virus
• Is a retrovirus

Question 7

What is the structure of HIV?

Answer 7

• Contains RNA and the enzyme reverse transcriptase
• The RNA and enzyme are surrounded by a capsid
• The capsid is surrounded by a lipid envelope containing glycoprotein spikes

Question 8

How is HIV transmitted?

Answer 8

• Sexual transmission
• Blood products
• Sharing of needles
• Mother to baby

Question 9

What is the process of HIV replication?

Answer 9

• The host cell for HIV is the helper T cell
• The attachment proteins of the HIV attach to specific receptors on the cell-surface membrane of the helper T cell
• The lipid envelope fuses with the cell-surface membrane, allowing viral RNA and the enzyme reverse transcriptase to enter the helper T cell
• The enzyme reverse transcriptase converts RNA to DNA
• Viral proteins are produced
• New HIV particles are assembled and released from the host cell

Question 10

What are the phases of HIV infection?

Answer 10

• Initial infection: the body produces HIV antibodies and cytotoxic T cells. This may cause a short flu-like illness with symptoms such as a skin rash and swollen glands
• Antibody-positive phase (HIV positive phase): this is the period after infection and before the onset of clinical signs, it can last from a few weeks to 13 years or more
• AIDS-related complex (ARC): the individual may suffer from opportunistic infections caused by bacteria, viruses or fungi, but the infections are not life threatening at this stage. A reduction in helper T cells may occur
• AIDS: this is the final stage where opportunistic infections and secondary cancers occur. AIDS-related death is commonly due to infections like tuberculosis or secondary cancers

Question 11

What are monoclonal antibodies?

Answer 11

• Identical antibodies produced by the clones of the same B cell

Question 12

Why are monoclonal antibodies used?

Answer 12

• To target medication to specific cell types by attaching a therapeutic drug to an antibody
• Medical diagnosis

Question 13

What are the advantages of monoclonal antibodies?

Answer 13

• The antibodies themselves are not toxic
• Highly specific, so only target a specific type of cell
• Fewer side effects compared to less specific treatments
• Smaller doses needed to be effective as they’re highly specific

Question 14

What are the disadvantages of monoclonal antibodies and vaccines?

Answer 14

• Animals are used in the production of monoclonal antibodies, which involves deliberately inducing cancer in them to generate tumour cells, causing them harm
• Vaccines must undergo animal testing before human trials, which raises ethical concerns
• Deciding who gets vaccinated first in the case of a new epidemic can be challenging

Question 15

Describe the role of antibodies in producing a positive result in an ELISA test

Answer 15

• First antibody attaches to antigen
• Second antibody with enzyme attached is added
• Second antibody attaches to antigen
• Substrate added and colour changes