topic 2 - antibodies in medicine

Question 1

what are monoclonal antibodies

Answer 1

antibodies produced from a single group of genetically identical b-cells (plasma cells)

Question 2

what are the seven points on how can you target drugs to a particular cell type (cancer cells)

Answer 2

(1) cancer cells have antigens called tumour markers they are not found on normal body cells
(2) monoclonal antibodies can be made that will bind to the tumour markers
(3) anti-cancer drugs are attached to the antibodies
(4) when the antibodies come into contact with the cancer cells they will bind to the tumour markers
(5) meaning the drug will only accumulate in the body where there are cancer cells
(6) the side effects of an antibody based drug are lower than other drugs as they accumulate near specific cells

Question 3

why are monoclonal antibodies identical in structure

Answer 3

because they are produced from a single group of genetically identical b-cells (plasma cells)

Question 4

what do pregnancy tests detect

Answer 4

the hormone human chorionic gonadotropin (hCG) - found in the urine of pregnant women

Question 5

what is the first step to targeting a particular substance for medical diagnosis (pregnancy test)

Answer 5

the application area contains antibodies for hCG bound to a coloured head

Question 6

what is the second step to targeting a particular substance for medical diagnosis (pregnancy test)

Answer 6

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

Question 7

what is the third step to targeting a particular substance for medical diagnosis (pregnancy test)

Answer 7

the urine moves up the stick to the test strip, carrying any beads with it

Question 8

what is the fourth step to targeting a particular substance for medical diagnosis (pregnancy test)

Answer 8

the test trip contains antibodies to hCG that are stuck in place (immobilised)

Question 9

what is the fifth step to targeting a particular substance for medical diagnosis (pregnancy test)

Answer 9

if there’s hCG present the test strip turns blue as the immobilised antibody binds to any hCG - concentrating the hCG antibody complex with the coloured beads attached - if no hCG is present the beads will pass through the test area without binging to anything and so won’t turn coloured

Question 10

what does ELISA stand for

Answer 10

enzyme-linked immunosorbent assay

Question 11

what is the ELISA test

Answer 11

a medical diagnostic test that uses antibodies

Question 12

what are two examples of what the ELISA test be used to test

Answer 12

pathogenic infection or allergies - anything you can make an antibody for

Question 13

how does the ELISA test work

Answer 13

an antibody is used which has an enzyme attached to it - this enzyme can react with a substrate to produce a coloured product - which causes the solution in the reaction vessel to change colour - if there’s no colour change it shows that the antigen or antibody of interest is present in the sample being tested

Question 14

what are the two different types of ELISA test

Answer 14

(1) direct ELISA - uses a single antibody that is complementary to the antigen you’re testing for
(2) indirect ELISA - uses two different antibodies

Question 15

what kind of ELISA test is used to test for HIV

Answer 15

indirect ELISA

Question 16

what is the first step of using an ELISA as an HIV test

Answer 16

HIV antigen is bound to the bottom of a well in a well plate (a plastic tray with lots of little circular pits in it)

Question 17

what is the second step of using an ELISA as an HIV test

Answer 17

a sample of the patient’s blood plasma (which may contain several different antibodies) is added to the well - if there’s any HIV-specific antibodies these will bind to the HIV antigen stuck to the bottom of the well - the well is then washed out to remove any unbound antibodies

Question 18

what is the third step of using an ELISA as an HIV test

Answer 18

a secondary antibody (that has a specific enzyme attached to it) is added to the well - this secondary antibody can bind to the HIV-specific antibody (which is also called the primary antibody) - the well is washed out again to remove any unbound secondary antibody - if there’s no primary antibody in the sample all the secondary antibody will be washed away

Question 19

what is the fourth step of using an ELISA as an HIV test

Answer 19

a solution is added to the well - this solution contains a substrate which is able to react with the enzyme attached to the secondary antibody and produce a coloured product - if the solution changed colour, it indicated that the patient has HIV-specific antibodies in their blood and is infected with HIV