topic 2 - antibodies in medicine Flashcards
cgp (topic 2C) 50 - 51
what are monoclonal antibodies
antibodies produced from a single group of genetically identical b-cells (plasma cells)
what are the seven points on how can you target drugs to a particular cell type (cancer cells)
(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
why are monoclonal antibodies identical in structure
because they are produced from a single group of genetically identical b-cells (plasma cells)
what do pregnancy tests detect
the hormone human chorionic gonadotropin (hCG) - found in the urine of pregnant women
what is the first step to targeting a particular substance for medical diagnosis (pregnancy test)
the application area contains antibodies for hCG bound to a coloured head
what is the second step to targeting a particular substance for medical diagnosis (pregnancy test)
when urine is applied to the application area any hCG will bind to the antibody on the beads, forming an antigen-antibody complex
what is the third step to targeting a particular substance for medical diagnosis (pregnancy test)
the urine moves up the stick to the test strip, carrying any beads with it
what is the fourth step to targeting a particular substance for medical diagnosis (pregnancy test)
the test trip contains antibodies to hCG that are stuck in place (immobilised)
what is the fifth step to targeting a particular substance for medical diagnosis (pregnancy test)
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
what does ELISA stand for
enzyme-linked immunosorbent assay
what is the ELISA test
a medical diagnostic test that uses antibodies
what are two examples of what the ELISA test be used to test
pathogenic infection or allergies - anything you can make an antibody for
how does the ELISA test work
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
what are the two different types of ELISA test
(1) direct ELISA - uses a single antibody that is complementary to the antigen you’re testing for
(2) indirect ELISA - uses two different antibodies
what kind of ELISA test is used to test for HIV
indirect ELISA
what is the first step of using an ELISA as an HIV test
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)
what is the second step of using an ELISA as an HIV test
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
what is the third step of using an ELISA as an HIV test
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
what is the fourth step of using an ELISA as an HIV test
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
