Mast cell degranulation in nasal polyps

Light- and electronmicroscopic observations as well as immunohistochemical studies were made on nasal polyps from 15 patients. The patients included 2 cases of aspirin intolerance (AA), 6 cases of allergic rhinitis (NA) and 7 cases of chronic rhinitis (CS) with negative skin tests against major inhalant allergens. Nasal polyps commonly contained many inflammatory cells such as neutrophils (PMN), eosinophils, plasma cells, mast cells, lymphocytes and macrophages. Two morphological features were conspicuous in our study: 1) PMN migration and attachment to the basal lamina, 2) accelerated degranulation of mast cells. Mean values of degranulated granules were 0.532473/micron2 in AA, 0.492615/micron2 in NA and 0.253591/micron2 in CS. These results indicate that mast cell degranulation in CS is much less than that in AA and NA. Immunohistochemical investigations revealed very few IgE-positive cells in both AA and NA, and none in CS. On the other hand IgG and IgA were frequently observed in all cases of nasal polyps. The present study suggests that mast cell degranulation plays an important role in the formation of nasal polyps, but it may not only be an IgE-dependent mechanism. To elucidate other possibilities, more extensive immunological studies will be required.