Page 34 - Veterinary Immunology, 10th Edition

combination of microbial-induced tissue damage as well as
VetBooks.ir inflammation that results in the set of animal behaviors that we call

sickness.
The innate immune system is a mixture of “hard-wired”

subsystems that lack any form of memory, and, as a result, each
episode of infection is treated identically. The intensity and
duration of innate responses such as inflammation therefore remain
unchanged no matter how often a specific invader is encountered.

These responses also come at a price: the pain of inflammation or
the development of sickness largely result from the activation of
innate immune pathways. On the other hand, the multiple
subsystems of the innate immune system are “on call” and ready to

respond immediately when invaders are detected (Fig. 1.4).

FIG. 1.4 The time course of innate and adaptive immunity. Surface
barriers provide immediate protection. Innate mechanisms provide
rapid protection that keeps microbial invaders at bay until adaptive
immunity can develop. It may take several days or even weeks for
adaptive immunity to become effective.

Adaptive Immunity

Inflammation and the other innate defenses are critical to the
defense of the body. Animals that fail to mount innate responses
will die from overwhelming infections. Nevertheless, these

responses cannot offer the ultimate solution to the defense of the
body. What is really needed is a defense system that can recognize

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