Allergic pulmonary and ocular tissue responses in the absence of serum IgE antibodies (IgE) in an allergic dog model

Allergen-specific serum IgE may be insensitive as a marker for IgE-mediated reactions at the mucosal level. Five of six atopic beagle dogs developed high ovalbumin (OVA)-specific serum IgE levels after sensitization. This study aimed to show that these dogs still express allergen-specific IgE at the pulmonary and ocular mucosal levels and in the skin even when corresponding serum IgE was below the detection limit. When serum IgE levels were negative, all dogs exhibited allergic reactions at the tissue level. Specifically, they displayed positive ocular reactions after an ocular OVA challenge. After airway challenge with aerosolized OVA, five out of six animals reacted with decreased compliance and increased resistance of the lungs. Furthermore, an eosinophilia in the bronchoalveolar lavage fluid (BALF) was observed. Four weeks after the last exposure to OVA, IgE-positive BALF cells were seen in all animals. Six weeks on, all dogs still displayed positive skin reactions to OVA. This indicates that not only skin testing but also detection of ocular and pulmonary allergic tissue reactions including cell-bound IgE in BALF can serve as more sensitive and lasting surrogate markers of hypersensitivity in the allergic dog model than detection of allergen-specific serum IgE levels.