AN ULTRASTRUCTURAL STUDY OF MAST CELLS IN THE ALVEOLAR WALL OF NORMAL AND ASTHMATIC LUNG

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Abstract
Specimens of normal and asthmatic lungs were studied at the electron microscopic level and the frequency and ultrastructural features of mast cells and their granules within the alveolar wall were assessed with morphometric techniques. The numerical density of mast cells per square millimetre of alveolar wall was 299 (SD = 258) in normal and 366 (SD = 260) in asthmatic lung. The mean area of the mast cell nucleated profile was 257 m2 (SD = 63) in normal lung and 298 (SD = 62) in asthmatic. The average number of secretory granules per single mast cell nucleated profile was 55 (SD = 13) in normal lung and 60 (SD = 12) in asthmatic lung. The diameter of the individual secretory granule was 3389 nm (SD = 426) in normal and 3456 (SD = 477) in asthmatic lung. The volume density of secretory granules in normal and asthmatic lung was 631 m3 and 581 m3respectively. The mean diameter of the individual subunit ("scroll") inside the secretory granule was 888 nm for both normal and asthmatic lung. In normal lung 642% of granules were of'scroll' and 'combined' type, and 358% of granules were "particulate" or 'empty'. In specimens from asthmatic patients 403% of granules had 'scroll' or 'combined' structures and 597% were 'particulate' or 'empty'. Our data suggest that there is no difference between the number of mast cells in normal and asthmatic lung. However, in pulmonary mast cells from asthmatic lung, degranulation is more common than in normal lung.