Increased metachromatic cells and lymphocytes in bronchoalveolar lavage fluid of dogs with airway hyperreactivity

Bronchoalveolar lavage (BAL) was performed in 11 basenji greyhound (BG) dogs, which showed persistent airway hyperreactivity to methacholine and citric acid aerosols, and in 15 non-BG dogs, which were significantly less reactive to these challenges. Five of the BG dogs hasd never received any aerosols prior to BAL, and 3 of the non-BG dogs were allergic to Ascaris suum. No dog received aerosols for 2 wk prior to BAL. Fluid recovered was centrifuged, and aliquots were taken for histamine content and cell identification. Total cell numbers were similar in BG and non-BG dogs. The BG dogs had increased percentages of lymphocytes and metachromatic cells in BAL fluid compared with those in non-BG dogs. Lymphocytes averaged 35.5 ± 2.3% (mean ± SEM) and 17.2 ± 1.2% (p < 0.005) in BG and non-BG dogs, respectively. The BG dogs that had received previous aerosol challenge and the BG dogs never challenged had 6.2 ± 0.4% (mean ± SEM) and 4.6 ± 0.6% metachromatic cells in BAL. Nonallergic non-BG dogs had 0.91 ± 0.2% and allergic non-BG dogs had 2.6 ± 0.5% metachromatic cells in BAL (p < 0.05 from BG). Total histamine closely correlated with numbers of metachromatic cells in BAL (r = 0.86). Forty-nine percent fewer mast cells were detected in cell preparations fixed in formalin than in cell preparations fixed in basic lead acetate. Electron micrographs revealed 2 mast cell types on the basis of structural characteristics of the granules. These differences in metachromatic cell and lymphocyte numbers between BG and non-BG dogs are unrelated to multiple aerosol challenges and underlying allergy and suggest that increases in metachromatic cell numbers in the airway lumen may be important in airway hyperreactivity.