Page 38 - Veterinary Immunology, 10th Edition

that has been previously vaccinated against tetanus (or has
VetBooks.ir recovered from tetanus), its serum separated and then injected into

a normal horse, the recipient animal will become temporarily
resistant to tetanus (Fig. 1.6).

FIG. 1.6 Immunity to tetanus can be transferred to a normal horse
by means of serum derived from an immunized horse. This clearly
demonstrates that antibodies in serum are sufficient to confer
immunity to tetanus in horses.

The protective molecules found in the serum of immune animals
are proteins called antibodies. Antibodies against tetanus toxin are

not found in normal horses but are produced following exposure to
tetanus toxin as a result of infection or vaccination. Tetanus toxin is
an example of a foreign substance that stimulates an adaptive

immune response. The general term for such a substance is antigen.
When an antigen enters an animal, the animal's B cells are
stimulated to produce antibodies that bind to that antigen and
ensure its destruction. Antibodies are highly specific and bind only
to the antigen that stimulates their production. For example, the

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