MAST-CELL NUMBERS ARE INCREASED IN THE SMOOTH-MUSCLE OF HUMAN SENSITIZED ISOLATED BRONCHI

The aim of this study was to examine the processes underlying the incr ease in responsiveness of human bronchus related to sensitization stat us by examining inflammatory cells in sensitized and nonsensitized tis sue. Sensitization status was determined in tissue from 26 subjects by detecting the presence or absence of contraction of bronchial rings t o common Australian allergens. Serial sections (6-mu m) of bronchial t issue were stained for mast cells, T lymphocytes, and eosinophils. The re was no significant difference between the total number of inflammat ory cells present in all locations (to a depth of 0.5 mm) of nonsensit ized (n = 14) and sensitized (n = 12) bronchi. Similar numbers of cell s were present in the two patient groups in epithelium, lamina propria , and adventitia. In contrast, there were significantly (p = 0.03) mor e inflammatory cells present within the smooth muscle of sensitized br onchi. A significantly (p = 0.04) greater number of mast cells in sens itized (9 [2-14]) versus nonsensitized (2 [0-8]) tissue was found in t his location (data are median with first and third quartile range). In addition there was a trend toward a greater area of smooth muscle in sensitized tissue. There results suggest that an interaction between s mooth muscle and inflammatory cells, especially mast cells, may play a role in bronchial hyperresponsiveness in vitro.