Antibodies in medicine + ELISA tests

Question 1

Monoclonal antibodies

Answer 1

Antibodies with the same tertiary structure produced from genetically identical plasma cells
So specific to one specific antigen

Question 2

Monoclonal antibodies use in medical treatments

Answer 2

Anti cancer medication

Question 3

Monoclonal antibodies use in medical testing

Answer 3

Pregnancy tests
ELISA tests

Question 4

Monoclonal antibodies use in cancer treatment

Answer 4

MABs that are specific to tumour markers (antigen) on cancer cells so bind to cancer cells to be detected +diagnosed
And also attached to anti cancer drugs to kill cancer cell

Question 5

What do pregnancy tests test for?

Answer 5

HCG protein which acts as antigen and it is only present in urine of pregnant women

Question 6

Pregnancy test kit description

Answer 6

Application area = Has specific antibodies which are complementary to HCG bound to a coloured bead
Test strip = immobilised antibodies specific to hCG

Question 7

What happens in case of a positive pregnancy test?

Answer 7

hCG from urine sample in application area binds to specific antibodies bound to beads (antibody-antigen complex)
Will move up strip to immobilised specific antibodies which binds to hCG and keeps it stuck with coloured beads

Question 8

Why is there a colour change in a pregnancy test?

Answer 8

Because coloured beads bound to antibodies bound to hCG will be immobilised by binding to immobilised antibodies causing colour change

Question 9

What happens in case of a negative pregnancy test?

Answer 9

No hCG bound to antibodies so immobilised antibodies will not bind to hCG so no colour change

Question 10

What does ELISA test stand for?

Answer 10

Enzyme linked immunosorbent assay test

Question 11

What do ELISA tests test for?

Answer 11

If there are antigens in patient using specific antibodies in the test (direct ELISA test)
If there are antibodies in patient using specific antigens in the test (indirect ELISA)

Question 12

2 types of ELISA test

Answer 12

Direct
Indirect

Question 13

Direct ELISAs test for?

Answer 13

A specific antigen in patient by using complementary antibodies in the test

Question 14

Indirect ELISAs test for?

Answer 14

A specific antibody in patient using antigens in the test

Question 15

Main reason ELISAs work?

Answer 15

Because it uses an antibody bound to an enzyme which when adding a substrate will form an enzyme substrate complex = colour change

Question 16

Direct ELISA description if the test is positive

Answer 16

Place fluid sample from patient which contains antigen on well (immobilised)
Detection complementary antibody added attached to enzyme which binds to antigen (immobilised)
Wash
Add substrate which binds to enzyme = colour change

Question 17

Direct ELISA description if the test is negative

Answer 17

Fluid sample is added but no antigen is present so not bound to well
Detection antibody with enzyme attached is added but will not be immobilised because no antigen present
So washed away
So when substrate added, no enzyme is present for E-S complex = no colour change

Question 18

Why is the test well washed?

Answer 18

To remove any antibodies that were NOT immobilised to bottom of the well so if test was negative no colour change would be observed
Prevents false positives

Question 19

When are indirect ELISAs used?

Answer 19

Mainly for HIV testing because HIV antigen usually hides in cells so hard to test for but the body produced HIV antibodies which are easier to test for

Question 20

Indirect ELISA description if test is positive

Answer 20

HIV antigen is bound to well
Sample of plasma with different antibodies inc HIV one is added which binds to HIV antigen (immobilised)
Wash then add secondary antibody with attached enzyme which binds to HIV specific antibody
Wash again then add substrate which forms E-S complex = colour change

Question 21

What happens if ELISA test is negative?

Answer 21

On washing, all antibodies are washed away so no HIV antibodies bound to antigen so no enzyme substrate complex formed when secondary antibody is added

Question 22

Ethical issues of MABs

Answer 22

Uses animal products
Uses animal testing

Question 23

Where are the antibodies bound to coloured beads found on the pregnancy test strip?

Answer 23

In the application area so immediately binds to antigen if present

Question 24

In a positive pregnancy test, what causes a positive result

Answer 24

If the HCG antigen is present it is bonded to the coloured bead antibody
Then the immobilised antibody at the positive test zone binds to the ANTIGEN = SANDWHICH

Question 25

In a pregnancy test, what causes the control zone?

Answer 25

Excess coloured bead antibodies not bound to antigen continue moving but immobilised by a different antibody further up the strip