* A hormone called HCG is found in the urine of pregnant women
* Pregnancy testing sticks detect this hormone. This is how they work:
* The bit of the stick you wee on has some antibodies to the HCG hormone with
blue beads attached.
* The test strip (which turns blue if you are pregnant) has some more antibodies
to the hormone stuck on to it, so they can’t move.
* The HCG hormone binds to the antibodies on the bit of the stick where you wee
and the antibodies on the test strip.
If you’re pregnant and you wee on the stick:
* The HCG hormone binds to the antibodies attached to the blue beads.
* The urine moves up the stick carrying the HCG hormone and the blue beads
with it.
* The blue beads and HCG hormone bind to the antibodies on the test strip –
so the antibodies get stuck on the test strip turning it blue – showing you
are pregnant.
If you’re not pregnant and you wee on the stick:
* The urine still moves up the stick carrying the blue beads. * But because there is no HCG hormone to bind to the antibodies on the test strip it doesn’t go blue.
* Different cells in the body have different antigens on their surface – so you can
make monoclonal antibodies that will bind to specific cells in the body.
* Cancer cells have antigens on their cell membrane that are not found on normal
body cells – they’re called tumour markers.
* In labs you can make monoclonal antibodies that will bind to these tumour
markers.
* An anti-cancer drug can be attached to these monoclonal antibodies. This might
be a radioactive substance, a toxic drug or a chemical which stops cancer cells
growing and dividing.
* The antibodies are given to a patient through a drip.
* The antibodies target specific cells (the cancer cells) because they only bind to
the tumour markers.
* The drug kills the cancer cells but doesn’t kill any normal body cells near the
tumour
