Serum Allergen-Specific Immunoglobulin E in Cats with Inflammatory Bronchial Disease

SIMPLE SUMMARY: To date, the etiology of feline chronic inflammatory bronchial disease, including feline asthma, chronic bronchitis, and mixed inflammatory forms, has not extensively been investigated. By measuring allergen-specific immunoglobulin E from the serum of cats with different types of inflammatory bronchial disease and healthy cats, we aimed to obtain information on serum reactions to environmental allergens. No significant differences were found in the number of positive immunoglobulin E-reactions between affected and healthy cats. Significantly, more cats with mixed airway inflammation reacted to mites. Sensitization to environmental allergens can be detected in healthy and diseased cats. Therefore, positive reactions must always be interpreted in the context of clinical signs and environmental conditions. ABSTRACT: The etiology of feline inflammatory bronchial disease is poorly understood. This study compares the degree of allergen-specific serum IgE responses between cats with feline asthma, chronic bronchitis, mixed inflammation, and clinically healthy cats (HCs). The retrospective case–control study used serum from eighteen cats with eosinophilic inflammation (EI), ten with neutrophilic inflammation (NI), six with mixed inflammation (MI), and fourteen HCs. Affected cats were categorized into groups based on bronchoalveolar lavage cytology. The measurement of IgE for 34 different allergens including fungal organisms, weeds, grasses, trees, mites, and insects was performed using an indirect ELISA. Positive reactions to allergens were detected in the serum of 17/18 cats with EI, 8/10 with NI, 6/6 with MI, and 11/14 HCs (p = 0.364). When overall positive reactions were compared between groups, cats with MI (p = <0.01) had significantly more positive reactions against mite allergens than HCs. Blood eosinophils inversely correlated with the absolute amount of allergen-specific serum IgE expressed in ELISA absorbance units (EAs) (p = 0.014). Sensitization against dust mites seems to be more prevalent in cats with MI. However, positive IgE reactions can be observed in healthy and diseased cats, and, therefore, need to be interpreted in the light of clinical findings and environmental conditions of individual patients.