15.7 urine and diagnosis

what hormones do pregnancy tests test for

hCG

how to make monoclonal antibodies

• a mouse is injected with hCG so it makes the appropriate antibody

• the B-cells that make the required antibody and then removed from the spleen of the mouse and fused with a myeloma, a type of cancer cell which divides very rapidly

• this new fused cell is known as a hybridoma

• each hybridoma reproduces rapidly. resulting in a clone of millions of ‘living factories’ which can produce the desired antibody

• these monoclonal antibodies are collected, purified and used in a variety of ways

the stages of a pregnancy test

• the wick is soaked in urine containing hCG

• the test contains mobile monoclonal antibodies that have very small coloured beads attached to them. They will only bond to hCG. If hCG is present in the urine, it will bind to the beads and form a hCG/ anitbody complex

• the urine carries on along the test structure until it reaches a window

• here there are immobolised monoclonal antibodies arranged in a line which only bind to the hCG/ antibody complex

• If the woman is pregnant, a line appears

• the urine continues up through the test to a second window

• there is a line of immobilised monoclonal antibodies that bind only to mobile antibodies, regardless of whether they are bound to hCG or not. This line shows whether the test is working

how to test for anabolic steroids

• vaporise the urine with a known solvent

• pass it along a tube

• the lining of the tube absorbs the gases and it analysed to give a chromatogram that can be read to show the presence of drugs

how are urine samples tested for drugs

• first sample may be tested by an immunoassay, using monoclonal antibodies to bind to the drug or its breakdown product

• if this is positive, a second sample may be ran through a gas chromatograph/ mass spectrometer to confirm the presence of the drug