Functional and morphologic characterization of mast cells recovered by bronchoalveolar lavage from Basenji greyhound and mongrel dogs

Abstract

Mast cells are believed to play an important role in the pathogenesis of asthma, and several investigators have suggested that increased numbers of mast cells in the airway lumen or increased releasability of histamine from these mast cells are responsible for chronic airway hyperreactivity. To determine whether mast cells in the lumen of the airways of hyperreactive Basenji greyhound (BG) dogs differ from those of mongrel dogs with normal airway reactivity, we investigated the morphologic and functional characteristics of mast cells recovered by bronchoalveolar lavage (BAL). BAL was performed in five BG and five mongrel dogs with 900 cc of a buffered salt solution. The recovered lavage fluid contained 115 ± 19 × 10 6 and 116 ± 14 × 10 6 (mean ± SEM) cells in BG and mongrel dogs, respectively. The proportion of all mast cells within the recovered cell population as enumerated after fixation with basic lead acetate and staining with alcian blue was not different in BG and mongrel dogs and averaged 0.80 ± 0.07% and 1.1 ± 0.3%, respectively. Typical mast cells as identified after fixation with paraformaldehyde were rare; however, significantly more mast cells were found in mongrel (0.03 ± 0.009%) than in BG dogs (0.004 ± 0.002%; p < 0.02). Mast cells recovered from BG and mongrel dogs were not different in their low spontaneous histamine release (2.0 ± 0.5% and 2.9 ± 0.8%), their histamine release on stimulation with the calcium ionophore A23187 (maximum release 44.8 ± 5.7% and 41.5 ± 3.9%), and their lack of response to compound 48 80 (maximum release 5.8 ± 1.8% and 6.1 ± 6.0%). The histamine content of all BAL cells was closely correlated to the total mast cell number ( p < 0.0001); the histamine content per mast cell averaged 1.80 ± 0.1 and 1.67 ± 0.07 pg in BG and mongrel dogs, respectively. These data demonstrate that hyperreactive BG dogs and mongrel dogs do not differ in the total number of mast cells recovered by BAL. Mast cells from BG and mongrel dogs are similar based on both morphologic and functional criteria and resemble atypical mast cells of rodents. These results do not support the hypothesis suggested by other investigators that the chronic bronchial hyperreactivity of BG dogs is due to airway mast cells. Differences in mast cells obtained by BAL from hyperreactive BG dogs compared to mast cells obtained from normal mongrel dogs may represent an epiphenomenon not necessary for the pathogenesis of chronic bronchial hyperreactivity.