The extracellular deposition of mast cell products is increased in hypertrophic airways smooth muscles in allergic asthma but not in nonallergic asthma

Background: Bronchial asthma is characterized by airways smooth muscle hypertrophy and infiltration of mast cells in the bronchial mucosa. The aim of this investigation was to study the distribution of mast cells in different compartments in the bronchial mucosa of allergic and nonallergic asthma in relation to airways remodeling. Methods: Bronchial biopsies were obtained from 29 subjects with allergic and nonallergic asthma and healthy controls. The biopsies were stained for mast cells by means of the tryptase specific antibody AA1. Extracellular deposition of mast cell products were judged on a semi-quantitative scale. Mast cells per mm(2) were counted in epithelium, lamina propria and the smooth muscle compartment. Smooth muscle was visualized by actin antibodies and the proportion of staining of the biopsy estimated. Laminin and tenascin layers were visualized by their respective antibodies. Results: Airways smooth muscle thickness was greater in allergic vs nonallergic asthma (P < 0.001). Mast cells were increased in all three compartments in both allergic and nonallergic asthma, with significantly higher numbers in smooth muscles in allergic asthma (P < 0.03). The extracellular deposition of mast cell products was more common in allergic than nonallergic asthma in lamina propria and smooth muscles (P = 0.025; P = 0.002, respectively). In patients with allergic asthma the numbers of mast cells with extracellular deposition of mast cell products were significantly correlated to the thickness of the laminin and tenascin layers. Conclusion: Our results suggest that there are large differences between allergic and nonallergic asthmatics as to mast cell activation and airways smooth muscle thickness. Our data implies that mast cells are causally involved in structural alterations in allergic asthma.