Page 1008 - Veterinary Immunology, 10th Edition

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FIG. 30.9 A panel of intradermal skin tests performed on a dog.
Each spot denotes a position where a small volume of dilute
allergen was injected intradermally. If the dog is allergic to that
allergen a local reaction characterized by redness and swelling
occur around the injection site. (Courtesy Dr. R. Kennis.)

Epidermal Barrier Dysfunction

In some cases of AD, the initial lesion may be a defect in epithelial
cells leading to skin barrier dysfunction. This permits loss of water

as well as the penetration of allergens and microbes and increases
contacts between the skin immune system and environmental
allergens (Fig. 30.10). Defects in either the skin barrier protein

filaggrin, or in skin lipids such as ceramides or sphingosine-1-
phosphate, may increase skin water loss and its susceptibility to
irritation. Atopic dogs may also show defects in the expression of
tight junction proteins such as occludin and zonula occludens 1
(ZO-1).

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