Page 338 - The Veterinary Laboratory and Field Manual 3rd Edition

Serology and immunology 307

antibody reacts. For example, antibody specific shape similar to the letter ‘Y’. Each arm of the
for the rotavirus antigen is called ‘anti-rotavi- ‘Y’ contains a binding site which reacts with the
rus’. The species of animal in which the antibody specific site (that is, antigenic determinant or
is raised will determine the nature and extent epitope) on an antigen (see Figure 6.4a).
of the antibody reaction. If rotavirus is inocu- The specific antigen–antibody reaction is a
lated into a pig and the pig produces antibody physical binding (Figure 6.4b). It can be com-
in response, the antibody would be called ‘pig pared to a lock and key fit, with the antibody
anti-rotavirus’ antibody. A wide range of pre- being the lock and the antigen the key. In this
pared antisera are now available commercially. way, the antibodies are able to inactivate anti-
gens. This can also make antigens more readily
phagocytized by white blood cells. The specific
Structure and function of antibodies immune system, in a healthy host previously
exposed to a range of antigens, is able to rec-
A typical antibody molecule consists of four pro- ognize and immediately respond to attack from
tein chains bound together so that they form a many potential pathogens.

Figure 6.4(b) Antigen–antibody binding
– precipitation. For the best reaction it is
important to add antibody and antigen at the
correct concentration. In many cases this
must be determined by using serial dilutions.
Source: M. Sarjoon Abdul-Cader, University
of Calgary, Canada.

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