Pregnancy

• Monoclonal antibodies are used in medical diagnosis, for example, in pregnancy tests.
• Pregnant women have the hormone hCG in their urine.
• A urine test strip has three parts with three different antibodies.
• The application area of the test strip has antibodies complementary to hCG, which are bound to a blue-coloured bead.
• The middle of the test strip has antibodies complementary to hCG-antibody complex.
• The end of the test strip has antibodies complementary to antibody without hCG attached.
• If pregnant, hCG binds to antibodies in the application area, forming a hCG-antibody complex.
• The hCG-antibody complex travels up the test strip and binds to antibodies at position 2, resulting in a blue line.
• If not pregnant, there is no hCG in urine, so hCG doesn’t bind to antibodies in the application area and doesn’t bind to antibodies at position 2, resulting in no blue line.
• Antibodies at the end of the test strip bind to hCG, resulting in a blue line.