monoclonal antibodies

Question 1

define monoclonal antibody

Answer 1

a single type of antibody that can be isolated and cloned

Question 2

give the 2 uses of monoclonal antibodies

Answer 2

1. targeted medication
2. elisa test

Question 3

what are the 2 types of targeted medication

Answer 3

1. direct monoclonal antibody therapy
2. indirect monoclonal antibody therapy

Question 4

explain how direct monoclonal antibody therapy works (4 marks)

Answer 4

1. cancer cell displays different antigens
2. monoclonal antibody designed with a binding site complementary to an antigen on cancer surface membrane
3. once bound antibody stops chemicals binding to cancer cell that stimulates cell division
4. this stops the cancer cell from growing

Question 5

outline the ethical issues associated with monoclonal antibodies

Answer 5

use mice to make tumour cells to produce a large number of monoclonal antibodies

Question 6

what are 2 uses of the elisa test

Answer 6

pregnancy testing

HIV testing

Covid antigen test

Question 7

explain how a pregnancy test works

Answer 7

1. woman urinates on stick
2. mobile antibody that has the dye attached is complementary to the hCG in the urine so the antibody binds to the hCG
3. 1st immobilised antibody with dye attached then binds to the hCG due to them being complementary

this results in the test line being positive

4. 2nd immobilised antibody is complementary to 1st mobile antibody with the dye so they bind together

resulting in a line on the control strip

Question 8

explain how monoclonal antibodies can be used to test for antigens
(6 marks)

Answer 8

1. test sample is attached to a slide
2. any unbound sample is washed off
3. add antibody to antigen we are testing for
4. wash off any unbound antibody
5. add 2nd antibody that is complementary to the 1st and
6. wash off any unbound antibody
7. add substrate

which produces a coloured product in the presence of an enzyme

colour change = antigen
no colour change = no antigen

intensity of colour change = indication of how much antigen present

Question 9

explain how vaccines work
( 4 marks)

Answer 9

vaccine contains antigens from pathogen

phagocyte presents antigens on it’s surface

Th cell with a complementary receptor binds to antigen

Th cell stimulates B cell with complementary antibodies on it’s surface to divide by mitosis to form a clone of cells called plasma cells that all produce the same antibody

plasma cells secrete a large number of identical antibodies

some B cells become memory cells that remain in the blood for a long time

Question 10

give 3 features of the primary immune response

Answer 10

plasma cells are short lived

antibodies remain in blood for longer

relatively slow process

Question 11

give 2 features of the secondary immune response

Answer 11

same antigen reinfects body

memory cells recognise the antigen and divide rapidly

into:
- more memory cells
- plasma cells
(release a larger number of antibodies very quickly which reduces damage to cells

Question 12

outline 4 differences between passive and active immunity

Answer 12

• active immunity involves memory cells passive immunity doesn’t
• active immunity involves production of antibodies from plasma cells
  passive immunity involves antibodies introduced in the body from another source
• active immunity is long term because antibody is produced in response to antigen
  passive immunity is short term because antibody is given and broken down
• active immunity is slower and passive immunity is faster

Question 13

higher mutation rate in a virus makes it harder to develop a vaccine

explain why

(3 marks)

Answer 13

1. mutation cause antigenic variability
2. vaccine contains specific antigen
3. antibody isn’t complementary to the new antigen