Immunity and Vaccines

Question 1

What are vaccines;?

Answer 1

Vaccines contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing disease. This means you become immune without getting any symptoms.

Question 2

What is herd immunity?

Answer 2

Herd immunity is when non-vaccinated people are less likely to catch the disease as the majority of people have been vaccinated, therefore there are fewer people to catch it from.

Question 3

What do vaccines always contain?

Answer 3

Antigens. These may be free or attached to a dead or attenuated (weakened) pathogen

Question 4

How can vaccines be recieved?

Answer 4

Through injection or orally.

Question 5

What are the disadvantages of taking a vaccine orally?

Answer 5

The vaccine could be broken down by enzymes in the gut or the molecules of the vaccine may be too large to be absorbed into the blood.

Question 6

What is antigenic variation?

Answer 6

This is when some pathogens can change their surface antigens

Question 7

What impact (s) does antigenic variation have?

Answer 7

Memory cells that have been produced from a first infection will not recognise the different antigens a second time. The immune system ahs to carry out a primary response against these new antigens.

Antigenic variation makes it difficult to develop vaccines against some pathogens for the same reason.

Question 8

What are some examples of pathogens that show antigenic variation?

Answer 8

HIV and influenza virus.

Question 9

How does antigenic variation affect the production of vaccines that aim to prevent people from catching influenza?

Answer 9

The influenza virus changes every year. This is because the antigens on the surface off the virus changes regularly, forming new strains of the virus.

Memory cells produced from vaccination with one strain of the flu will not recognise other strains with different antigens.

New vaccines are developed and one is chosen every year that is most effective against the recently circulating influenza virus.

Question 10

What is active immunity?

Answer 10

Type of immunity you get when your immune system makes its own antibodies after being stimulated by an antigen.

Question 11

What are the 2 different types of active immunity?

Answer 11

Natural- when you become immune after catching a disease

Artificial- when you become immune after being given a vaccination

Question 12

What is passive immunity?

Answer 12

Type of immunity you get from being given antibodies made by a different organism and your immune system doesn’t produce any antibodies of its own.

Question 13

What are the 2 types of passive immunity?

Answer 13

Natural- when a baby becomes immune due to the antibodies it receives from its mother through the placenta and breast milk

Artificial- when you become immune after being injected with antibodies from someone else

Question 14

What are monoclonal antibodies?

Answer 14

Monoclonal antibodies are antibodies produced from a single group of genetically identical B cells. This means they are all identical in structure.

Question 15

How can monoclonal antibodies be used to target cancer cells?

Answer 15

Cancer cells have antigens called tumor markers.

Monoclonal antibodies can be made that will bind to the tumor markers.

When the antibodies come into contact with the cancer cells they will bind to the tumor markers.

Means the drug will only accumulate in the body where there are cancer cells.

Question 16

How can monoclonal antibodies be used for pregnancy tests?

Answer 16

1) Application area contains antibodies for hCG bound to a blue, coloured bead.

2) When urine is applied to the application area any hCG will bind to the antibody on the beads, forming an antigen-antibody complex

3) The urine moves up the stick to the test strip, carrying any beads with it.

4) The test strip contains antibodies in hCG that are immobilised.

5) If there is hCG present the test strip turns blue because the immobilised antibody binds to any hCG. If no hCG is present the beads will pass through the test area without binding to anything and so it won’t go blue

Question 17

What are the stages of using an ELISA test for HIV?

Answer 17

1) HIV antigen bound to the bottom of the well

2) Plasma sample added. There are antibodies that attach to the HIV, so it is specific to HIV. There are also antibodies present that aren’t specific to HIV.

3) A secondary antibody is added. This secondary body has an attached enzyme

4) A solution is added to the well, which is able to react with the enzyme attached to the secondary antibody and produce a coloured product. If the solution changes colour it indicates that the patient has HIV specific antibodies in their blood and is infected with HIV

Question 18

What is the structure of a HIV virus?

Answer 18

• A core that contains the genetic material, including the enzyme reverse transcriptase, which is needed for virus replication.
• An outer coating of protein called a capsid
• An extra outer layer called an envelope. This is made of membrane stolen from the cell membrane of a previous host cell
• Sticking out from the envelope are loads of copies of an attachment protein that help HIV attach to the host helper T cell.

Question 19

Where and how does HIV replicate?

Answer 19

HIV replicates in helper T cells

The stages of replication are:

1) Attachment protein attaches to a receptor molecule on the cell membrane of the host helper T cell

2) Capsid released into cell, where it uncoats and releases the genetic material into the cell’s cytoplasm

3) Inside the cell, reverse transcriptase is used to make a complimentary strand of DNA from the viral RNA template for more DNA and RNA.

4) Double stranded DNA is made and inserted into the human DNA

5) Host cell enzymes are used to make viral proteins from the viral DNA within the human DNA

6) Viral proteins assembled into new viruses.

Question 20

Why don’t antibiotics work against viruses?

Answer 20

Antibiotics kill bacteria by interfering with their metabolic reactions
They target the bacterial enzymes and ribosomes used in these reactions

Viruses don’t have their own enzymes and ribosomes , they use the ones in the host cells. So because human viruses use human enzymes and ribosomes to replicate, antibiotics can’t inhibit them because they don’t target human processes.