Bronchoalveolar Eosinophilic Cells in a Canine Model of Asthma: Two Distinctive Populations

Abstract

In a canine model of asthma, the identity and relationships of two types of cells with eosinophilic granules found in bronchoalveolar lavage (BAL) were investigated. Five female and three male newborn mongrel dogs were sensitized by intraperitoneal injection of 500 μg ragweed in 30 mg aluminum hydroxide repeated weekly for 8 weeks and then biweekly until 16 weeks of age. Three female and two male littermate controls received 30 mg aluminum hydroxide. From 4 months of age, dogs received six breaths of wet-nebulized ragweed solution through an endotracheal tube bimonthly. Bronchoalveolar lavage was performed 2 months or more after the last exposure to ragweed and was repeated 5 hours after ragweed inhalation. Dogs studied were 15 to 38 months of age. Eosinophilic cell populations were determined in BAL and peripheral blood; cells were examined by light and electron microscopy. Two eosinophilic cell types were in BAL: an eosinophil and an atypical cell with globule leukocyte characteristics. Specific microgranules, a constant feature of eosinophils, were prominent in the atypical cell and suggest a relationship to the eosinophil granulocyte series for the atypical cell and cells identified by others as globule leukocytes. In ragweed sensitized animals, there were more eosinophilic cells in BAL fluid and more eosinophils in peripheral blood. There was a proportional increase in BAL eosinophils 5 hours after ragweed inhalation and a corresponding decline in peripheral blood eosinophils. There was no increase in numbers of eosinophils in the sensitized animals; eosinophil and atypical cell numbers in littermate controls were unchanged.