MSD Manual

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Professional Version

Overview of Immunologic Diseases in Animals


Ian Rodney Tizard

, BVMS, BSc, PhD, DSc (Hons), DACVM, Department of Veterinary Pathobiology, College of Veterinary and Biomedical Sciences, Texas A&M University

Reviewed/Revised Jan 2024

The function of the immune system is the detection and destruction of invading microorganisms and abnormal cells. Because of the great diversity of microbial invaders, the immune system is a complex mixture of protective mechanisms. These may be simply classified as innate immunity Innate Immunity in Animals Innate immunity is one of two main immunologic strategies found in animals, the other being adaptive immunity. Major functions of the innate immune subsystem include anatomic defenses against... read more and adaptive immunity Adaptive Immunity in Animals Innate immune responses, although critical to the defense of the body, cannot guarantee protection. They lack the flexibility to respond optimally to a diverse set of microorganisms, and they... read more . Immediate protection within the first few hours and days of microbial invasion is the responsibility of the “hardwired” innate immune system. Longer-term protection is the responsibility of the adaptive immune system.

In general, immune system disease takes three forms:

Some inflammation and limited tissue destruction are features of the normal innate and adaptive immune responses. Clinical disease occurs when this inflammation is excessive, in the wrong place, or directed against the wrong target.

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