Objective: To evaluate a model for atopic dermatitis (AD) and to measure the effect of sensitization in Beagles genetically predisposed to produce high serum concentrations of allergen specific IgE.
Animals: 22 laboratory Beagles.
Procedure: Seventeen dogs were sensitized from birth to 3 allergens (recombinant birch pollen, Dermatophagoides pteronyssinus, and D farinae). Five nonsensitized dogs from the same litters served as controls. Clinical scoring, regular intradermal testing, measurement of serum concentrations of allergen-specific IgE, and collection of biopsy specimens of skin at 23, 32, and 43 weeks of age were performed. Serial tissue sections were stained for identification of IgE+ cells, mast cells and their subtypes, T-cells, Langerhans cells, and major histocompatibility complex class-II+ cells. At the age of 15 months, dogs were continuously exposed to 2 microg of mite allergen/g of dust.
Results: Sensitized dogs had positive intradermal test reactions and significantly higher serum concentrations of allergen specific IgE, compared with nonsensitized dogs. In sensitized and nonsensitized dogs, a significantly higher number of mast cells was found at predilection sites, compared with the control biopsy site. The number of mast cells at predilection sites increased with age. Sensitization significantly increased the number of epidermal Langerhans cells by 23 weeks of age. The number of epidermal Langerhans cells significantly increased in nonsensitized dogs by 32 weeks of age. Clinical scoring only revealed mild transient erythema in some dogs.
Conclusions: increases in concentrations of serum allergen-specific IgE and exposure to allergens is not sufficient to induce clinical signs of AD in genetically predisposed dogs.