Respiration

ELISA tests are carried out in special plates that have an ordered arrangement of wells on their surface

The following outlines one way in which an ELISA test can be used to find a pathogen in a
person’s blood serum

Each well of the plate is coated with the antigen of the specific disease which is being
looked for

The well is then washed to remove surplus antigen

The patient’s serum is added to the well

Any antibodies specific to the disease will bind to the antigens at the bottom of the
well

The well is then washed again to remove any antibodies that have not attached
themselves to antigens

An antibody complex is then added.  This can be a fluorescent marker or a
radioactive marker; in the case of ELISA, an enzyme is added

The antibody complex (enzyme) binds to the antibody

The well is washed again to remove any unbound enzymes

Finally a substrate is added and is converted by the enzyme into a coloured product

The colour change indicates the presence of the pathogen