Page 1404 - Veterinary Immunology, 10th Edition

antibodies in the serum will bind to the antigen layer. After
VetBooks.ir incubation and washing to remove unbound antibody, the presence

of bound antibodies can be detected by adding a solution
containing an antiglobulin chemically linked to an enzyme. This

labeled antiglobulin binds to the antibody and, following
incubation and washing, can be detected and measured by adding a
solution containing the enzyme substrate. The enzyme and
substrate are selected to ensure that a colored product develops in

the tube. The intensity of the color that develops is therefore
proportional to the amount of enzyme-linked antiglobulin that is
bound, which in turn is proportional to the amount of antibody
present in the serum under test. The color intensity may be

estimated visually or by spectrophotometry. The sensitivity of the
assay depends on the affinity of the antibodies and the detection
system used. It is also affected by nonspecific binding of antibodies
to the plastic surface.

FIG. 42.6 The indirect ELISA technique. Antigen is bound to the

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