Antibodies/ELISA test Flashcards
What are antibodies? (3)
- Quarternary structure proteins (4 polypeptides)
- Secreted by B lymphocytes e.g. plasma cells in response to specific antigens
- Bind specifically to antigens forming antigen antibody complexes
Describe the structure of an antibody (8)
Also try to imagine what an antibody looks like as if you were labelling it
Antigen
Antigen binding site
Variable region
Constant region
Disulfide bridges
Light chain
Heavy chain
Hinge region
Explain how antibodies lead to the destrution of pathogens? (5)
- Antibodies bind to antigens on pathogens forming an antigen-antigen complex
-Specific tertiary structure so binding site/variable region binds to complemntary antigen
*Each antibody binds to 2 pathogens at a time causing agglutination(clumping) of pathogens - Antibodies attract phagocytes
- Phagocytes bind to the antibodies and phagocytose many pathogens at once
Explain the diff between primary anf secondary immune response (7)
- Primary-First exposure to antigen
-Antibodies produced slowly at a lower conc
-Takes time for specific plasma B cells to be stimulated to produce specific antibodies
-Memory cells produced - Secondary-Second exposure to antigen
-Antibodies produced daster and at a higher conc
-B memory cells rapdi;y undergo mitosis to produce many plasma cells which produce specific antibodies
What happens when there is a mutation in the gene which codes for an antigen
The pathogens DNA will mutate which changes the shape of the antigen—>Any previous immunity to this pathogen is no longer effective as the memory cells of the previous pathogen would have a diff shape
What is the variable region
The binding site of an antibody that is different for every antibody
-Binding site consists of a sequence of amino acids that form a specific 3D shape that binds to a specific antigen
What is the constant region
The rest of the antibody that is not the variable region
-This binds to recpetors on cells such as B cells
How do antibodies lead to destruction of an antigen (there are two ways this can happen) (3)
*The cause agglutination of the bacterial cells
-Agglutination-Antibodies bind to two antigens and it clumps them together–>Making it easier for phagocytes to locate and destroy the pathogens
*They then serve as markers that stimulate phagocytes to engluf the bacterial cells to which they are attached
What are monoclonal antibodies
Identical antibodies that have been produced by different B cells that have been cloned from a parent cell
What happens in direct monoclonal antibody therapy
Monoclonal antibodies are produced that are specific to antigens on cancer cells
These antibodies are given to a patient and attach themselves to other receptors on their cancer cells
They attach to the surface of their cancer cells and block the chemical signals that stimulate their uncontrolled growth
What is indirect monoclonal antibody therapy
Involves attaching a radioactive or cytotoxic drug to the monoclonal antibody
When the antibody attaches to the cancer cell it kills them
What are the ethical issues of using monoclonal antibodies
Production of monoclonal antibodies involves the use of mice ro produce antibodes and tumor cells
The production of tumor cells involves deliberttly inducing cancer in mice
Monoclobal antibodies have been used to successfully treat many diseases saving many lives However there have also been multiple deaths associated with their use
Testing for the safety of new drugs presents danger.
Distinguish between an antibody and antigen
An antigen is a molecule that triggers an immune response while an antibody is the molecule that has a complemnetray shape to the antigen andis prodcued in response to it
Explain th euse of antibodies in the ELISA(Enzyme-linked Immunosorbent Assay) test to detect antigens?
- attach sample with potenial antigens to well
- add complementary monoclonal antibodies woth enzyme attached–> bind to antigens if present
- wash well–> remove unbound antibodies (to prevent false positive)
- Add substrate–> enzymes create products that cause a colour change (positive result)
Explain th euse of antibodies in the sandwich ELISA(Enzyme-linked Immunosorbent Assay) test to detect antigens?
- attach sample with potenial antigens to well
- Add sample with potential antigens,then wash well
- add complementary monoclonal antibodies with enzymes attached –>bind to antigens if present
- Wash well-Remove unbound antibodies to prevent false positives
- Add subsrate–> enzymes create products that cause a colour change (positive result)
Explain the use of antibodies in the ELISA test to detect antibodies
- attach sample with potenial antigens to well
- Add sample with potential antibodies ,wash well
- add complementary monoclonal antibodies with enzymes attached –> bind to antibodies if present
- Wash well–>remove unbound antibodies
- Add substrae-Enzymes create products that cause a colour change
Suggest the purpose of a control well in the ELISA test
Compare to test to show only enzymes cuase colour change
Compare to test to show all unbound antibodies have been washed away
Discuss some general ethical issues associated with th euse of vaccines and monoclonal antibodies
Pre clinical testing on/use of animals- potential stress/harm/mistreatment
-But animals not killed and helps produce new drugs to reduce human suffering
Clinical trials on humans-potenital harm/side effetcs
Vaccines may continue high risk activities and still develop/pass on pathogens
Use of drug- potentially dangerous sie effects
Suggest some points to consider when evaluating methodlogy relating to the use of vaccines and monoclonal antibodies
Was the sample size large enoguh to be representive
Were particpants diverse in terms of age,sex,ethnicity and health status
Were placebos /control groups used for comparison
Was the duration of the study long enought o show long term effects
Was the trial double nlind (nether doctor nor paiteint knew who was given the dyrg or placebo)to reduce bias
Suggest some points to consider when evaluating evidence and date relatong to the use of vaccines and monoclonqal antiodies
What side efects were pbserved, and how frequent did the y occur
Was a statistical test used to see if there was a sgnificant diff between start and final results
Was the standard devoation of final results large ,shjwoing there may not be a sig diff
What dosage was optimum?Does incfreasing effectiveness epugh to justify extra cost?
Was the cost of production and distrubtion low enough
