Page 685 - Veterinary Immunology, 10th Edition

Immunity to Food, 246
VetBooks.ir Vaccination on Body Surfaces, 246

LEARNING OBJECTIVES

After reading this chapter, you should be able to:

• Describe the immune defenses of the skin.
• Describe the immune defenses of the mammary gland and explain its
vulnerabilities.

• Understand that the intestine is the largest immune organ in the animal body.
• Describe briefly the major defense mechanisms of the respiratory tract.
• Describe the defenses of the genitourinary system.

• Describe the basic features and properties of immunoglobulin A (IgA).
• Understand how surface defenses such as IgA exclude invaders by preventing
them from binding to surface epithelia.

• Explain why γ/δ T cells are specialized for epithelial defense.
• Explain the role of IgA in preventing microbial invasion.

• Discuss the concept that IgE is a backup surface defense molecule.
• Describe briefly the phenomenon of oral tolerance.
• Define M cells, Paneth cells, intraepithelial lymphocytes, γ/δ T cells, inductive
sites, and immune exclusion.

Although mammals possess an extensive array of innate and
adaptive defense mechanisms within tissues, it is at their surfaces
that invading microorganisms are first encountered and largely
repelled or destroyed (Fig. 22.1). Although the skin is the most

obvious of these surfaces, it in fact represents only a small fraction
of the area of the body exposed to the exterior. The surface areas of
the mucous membranes of the intestine and respiratory tracts are at
least 200 times larger. The majority of pathogens enter the body

through mucosal surfaces when ingested or inhaled, and
respiratory and enteric infections are the most significant causes of
death in young animals. While the immune systems ensure that the

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