In vitro allergen-induced degranulation of pulmonary mast cells from horses with recurrent airway obstruction (heaves)

Abstract

Objective - To determine the capacity of pulmonary mast cells (PMC) to degranulate in response to various potential allergens and other secretagogues in horses with recurrent airway obstruction (heaves) and clinically normal horses before and after exposure to moldy hay. Animals - 5 horses with heaves and 5 clinically normal horses. Procedures - Heaves was characterized as an increased clinical respiratory score and maximum change in transpulmonary pressure of > 20 cm H2O after exposure. Bronchoalveolar lavage was performed during each period. Washed and resuspended cells were exposed for 20 minutes at 37 C with whole reconstituted freeze-dried preparations of Aspergillus fumigatus, Alternaria tenuis, and Ambrosia elatior, fungal extracts of Aspergillus fumigatus, Alternaria tenuis, and Micropolyspora faeni; A23187; and compound 48/80. Histamine release (HR) was used as a marker of degranulation. Results - Compared with clinically normal horses, HR was significantly greater from PMC from horses with heaves during remission and exacerbation in response to whole preparations and extracts of Aspergillus fumigatus and whole preparations of Alternaria tenuis. Extracts of Alternaria tenuis caused significantly greater HR from PMC from horses with heaves during exacerbation. Histamine was also released from PMC in response to A23187 and to changes in osmolality of the medium, but only as a result of cell lysis by compound 48/80. Conclusions - Increased degranulation of PMC after antigenic challenge may contribute to the pathogenesis of heaves in horses. Clinical Relevance - Strategies for prevention and treatment that attenuate degranulation of PMC may assist in the clinical management of horses with heaves.