2.4.3: Antibodies Flashcards
Describe the structure of an antibody
proteins, y shaped, globular protein - specific 3D structure, quaternary structure - 4 polypeptide chains, 2 light and 2 heavy joined by disulfide bridges. Antibody has 2 regions - constant region (same primary structure), variable region (different primary structure). The variable region is the antigen binding site.
what is a pathogen
a disease causing microorganism
what is an antigen
a foreign protein that causes an immune response
give 5 actions that antibodies carry out
1 - cause bacterial lysis
2 - coat pathogen to aid phagocytosis
3 - deactivate flagella to aid phagocytosis
4 - prevent pathogens/toxins entering host cells
5 - cause pathogen to agglutinate (clump, can be engulfed in one go)
What are monoclonal antibodies (mAbs)
artificial antibodies produced in a lab specific to one type of antigen
How are mAbs made and
why is a myeloma cell used
1 - inject small mammal with antigen to stimulate humoral response to release B lymphocytes
2 - Isolate the plasma B cells that secrete the antibodies in response to injected antigen
3 - Fuse plasma cell with myeloma cell (cancer cell) to form a hybridoma because mitotic rate of myeloma cell is far greater than that of plasma cell
4 - isolate hybridoma that produces the correct antibody for the antigen
5 - clone the specific hybridoma to produce many monoclonal antibodies
What are the advantages of using monoclonal antibodies in treatment
mAbs are non-toxic
mAb are specific and so lower dosage of drug is needed - cheaper, fewer side effects
How does direct mAb therapy work
mAb attaches to cancer cell receptor which prevents cell signalling
How does indirect mAb therapy work
Magic bullet (mAb with drug attached) attaches to cancer cell antigens -> apoptosis of cancer cell. Body cells remain untouched as the specific antigen is not present on patient’s body cell
Describe how a pregnancy test works
SAME AS COVID TEST
1 - Urine containing hCG (hormone produced by placenta) contacts dipstick
2 - Dipstick containing hCG mAbs with blue latex particle attached binds to hCG from urine and the mAbs move up the dipstick
3 - A row of immobilised mAbs bind to any hCG mAbs with hCG attached, if a blue line in this position presents - WOMAN HAS A BABY WOOHOO
4 - A row of immobilised mAbs at a point higher bind to any hCG mAbs that don’t have hCG attached, a blue line in this position acts as a control
what test is used to test for PSA - prostate specific antigen
ELISA test - Enzyme Linked ImmunoSorbent Assay
what is PSA
prostate specific antigen - protein found in the blood of people with prostate cancer
How does a direct ELISA test work when testing for PSA
1 - Attach a mAb specific to PSA to a well in a test plate. wash test plate to remove any unbound 1st mAb
2 - add patient’s blood sample, if PSAs are present, they’ll bind to 1st mAb. wash test plate to remove any unbound antigens
3 - add 2nd mAb specific to PSA with an enzyme attached. was test plate to remove any unbound 2nd mAb
4 - add colourless substrate that reacts with the enzyme, if there is a visible colour change, PSA is present, the stronger the colour, the higher the concentration of PSA there is
what is the difference between a direct and an indirect ELISA test
in a direct ELISA test, you add the 1st mAb, then blood sample, then 2nd mAb with enzyme attached.
whereas in an indirect ELISA test, you add blood sample, then 1st mAb, then 2nd mAb with enzyme attached
give 3 points regarding the ethics of using mAbs
1 - small mammals are used to produce mAbs, myloma cells - induce cancer
2 - requires informed consent from patients (mAbs treatment is quite new)
3 - Failed drug trials
