Immune system

Question 1

Why can elisa test not be used to diagnose AIDS?

Answer 1

Can only be diagnosed through AIDS related symptoms

Number of helper T cells in body

Question 2

Elisa test solution will remain yellow if a person is not infected with HIV. Explain why.

Answer 2

No HIV antibody present

Secondary antibody will not bind

Question 3

Why does a baby whos mother has HIV and who tests positive for HIV not prove the baby is infected with HIV

Answer 3

Children receive antibodies from their mothers antibodies

Solution will always be blue

Question 4

Why is it important for there to be a control well in ELISA test?

Answer 4

To make sure all unbound antibody is washed away

To ensure only antibodies cause change in colour

Question 5

People with AIDS die because they are unable to produce an immune response to
pathogens (lines 2-4).
Explain why this leads to death

Answer 5

Infected by pathogen
Pathogen reproduces
Damages cells and releases toxins

Question 6

Explain why HIV rapidly entering host cells means that a vaccine might not be effective against HIV.

Answer 6

1. HIV enters cells before antibodies can bind to it;

2. Antibodies cannot enter cells to destroy HIV

Question 7

Explain why HIV showing a lot of antigenic variability means that a vaccine might not be effective against HIV.

Answer 7

Antigen on HIV changes;

2. Specific antibody no longer binds to new antigen;

Question 8

Suggest why some vaccines may be considered unsafe

Answer 8

Inactive virus may become active

Non-pathogenic virus may mutate and harm cells

Question 9

What is an antigen

Answer 9

A foreign protein that causes an immune response

Question 10

Describe how B-lymphocytes respond when they are stimulated by antigens.

Answer 10

divide by mitosis
produce plasma cells;
plasma cells make antibodies;
plasma cells produce memory cells

Question 11

Why can a glycoprotein act as an antigen?

Answer 11

Different shape to body proteins

Question 12

The percentage of the population vaccinated does not need to be 100% to be effective in
preventing the spread of whooping cough.
Suggest why.

Answer 12

More people are immune

2. Unvaccinated people less likely to contact infected people.

Question 13

Putting bee honey on a cut kills bacteria. Honey contains a high concentration of
sugar.
Suggest how putting honey on a cut kills
bacteria.

Answer 13

Water potential is higher in cells than in honey
Water leaves the bacteria
This stops metabolic reactions

Question 14

Explain why this virus can be described as inactive

Answer 14

No more cells infected

2. Because virus is not replicating

Question 15

Explain an advantage of programmed cell death?

Answer 15

Prevents replication of virus

Question 16

How does phagocytosis of a virus lead to the presentation of its antigens?

Answer 16

1. Phagosome fuses with lysosome;
2. Virus destroyed by lysozymes
3. Antigen from virus are displayed on the cell membrane;

Question 17

Scientists have found a virus that produces a protein very similar to human
collagen.
Suggest how the immune response to this viral protein can result in the
development of RA.

Answer 17

The antibody against virus antigen will bind
to collagen;
This results in the destruction of the (human)
cells/collagen;