Page 1351 - Veterinary Immunology, 10th Edition

In obese animals, this widespread macrophage activation
VetBooks.ir predisposes to inflammatory diseases such as atherosclerosis,

arthritis, type 2 diabetes mellitus and autoimmunity, as well as to
cancer. There is thus a clear link between obesity and chronic low-

grade inflammation. Given the increasing obesity of pets as well as
some of the effects of rapid growth in food animals, veterinarians
would be well advised to take this link into account.
Leptin also enhances NK cell development and activation. It

promotes Th1 cell production of IFN-γ, TNF-α, and leptin itself,
thus generating an autocrine feedback loop. In lean animals where
leptin levels are low, macrophage activation is suppressed,
inflammatory responses are reduced, and there is a shift from Th1

to Th2 responses while increasing Treg cells.
Adiponectin counteracts the activities of leptin. Its concentration
is inversely related to body weight, and it has strong
antiinflammatory activity. In lean animals, it decreases production

of IL-8, IFN-γ, IL-6, and TNF-α while increasing the production of
IL-1RA and IL-10. It induces maturation and activation of dendritic
cells. As a result, it reduces Th1 and Th17 responses. Adiponectin
also regulates glucose and fatty acid metabolism. In obesity,

adiponectin production drops, and adipose tissue macrophages
then produce a cytokine called resistin that increases insulin
resistance leading to diabetes.

Trace Elements
Several trace elements are required for optimal functioning of the

immune system. The most important are zinc, copper, selenium,
and iron. Deficiencies of any of these are immunosuppressive. Zinc
is especially critical to the proper functioning of the immune system

since it acts as an ionic signaling messenger to promote T cell
activation. Zinc-deficient pigs have reduced thymus weight,
depressed cytotoxic T cell activity, depressed B cell activity,
depressed NK cell activity, and decreased antibody production. If
pregnant animals are deprived of zinc, their offspring are

immunosuppressed. Neutrophils from zinc-deficient animals have
reduced chemotaxis and phagocytosis. Mild zinc supplementation
may promote immunity. On the other hand, because many bacteria

utilize zinc, the body also sequesters it to limit its availability

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