Page 1003 - Veterinary Immunology, 10th Edition

mites (Dermatophagoides farinae and D. pteronyssinus), animal
VetBooks.ir danders, and the yeast Malassezia pachydermatis. There are no

significant clinical differences between food-induced AD and that
associated with environmental allergens.

Skin Lesions, Cells, Cytokines, and Chemokines

It was long believed that AD was an allergic reaction to inhaled
antigens despite the fact that respiratory signs are not commonly
associated with the disease. It is more likely, however, that allergen
exposure occurs through the skin. Antigens are trapped by

Langerhans cells and then presented to γ/δ T cells. T cells appear to
play a critical role in the pathogenesis of AD, with type 2 responses
predominating in the first 24 hours and mixed type 1 and 2

responses in the later, chronic disease (48–96 hours) (Fig. 30.7).
Lesions from patients with both forms of AD are infiltrated with T
cells and dendritic cells. However, Th17- and Th22-derived
cytokines are elevated only in those with intrinsic AD. Conversely,
lesions from patients with extrinsic AD have higher Th2 cytokines

(IL-4, IL-13, and IL-5). The suppressive cytokine TGF-β is
underexpressed in both.

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