The proliferative activity of mast cells in the nasal mucosae of allergic (n = 14) and non-allergic (n = 18) rhinopathic patients was studied by a sequential double immunohistochemistry using anti-proliferating cell nuclear antigen (PCNA) and anti-tryptase antibodies. Two hundred to 300 tryptase-positive cells (mast cells) were studied in each allergic nasal epithelium. In case of non-allergic nasal mucosa, only a few mast cells existed in the epithelial layer. The total number of mast cells which we could detect in all patients was 168 cells. One of these cells contained PCNA. Three hundred to 500 mast cells were studied in each subepithelial layer and deep layer of lamina propria of both diseases. PCNA-positive mast cells were observed in the nasal epithelia of 10 allergic patients. In the subepithelial layer, PCNA-positive mast cells were observed eight allergic patients and four non-allergic patients, respectively. In the deep lamina propria, PCNA-positive mast cells were observed in a few patients with both diseases. The percentage of PCNA-positive mast cells of all mast cells each area ranged from 0 to 1.7%. The incidence of PCNA-positive mast cells was statistically higher in the allergic epithelium and subepithelial layer than in the deep layer of lamina propria. Moreover, that of PCNA-positive mast cells in the subepithelial layer was higher in allergic than in non-allergic nasal mucosa. Our results suggest that mast cell proliferation may contribute to the number of mast cells in the nasal epithelium and subepithelial layer of allergic patients.

The accumulation of mast cells in the allergic nasal epithelium is well known, yet the mechanism remains unclear. We studied whether there is a candidate for mast cell progenitors in the allergic nasal mucosa tissue removed at the time of surgery. We first confirmed that most mast cells in nasal mucosae of 10 nasal allergic patients had c-kit receptor by immunohistochemistry using the mirror sectioning technique. We then investigated whether c-kit receptor+, tryptase–, IgE– cells existed in nasal mucosae of 15 nasal allergic patients and 15 nonallergic ones using sequential triple immunohistochemistry. We observed the area in which 1,000 to 1,100 tryptase-positive cells (mast cells) existed in both the subepithelial layer and the deep layer of each nasal lamina propria. The epithelial layer above this area was also examined. Some c-kit receptor+, tryptase– cells existed in the nasal mucosae of 11 patients with nasal allergy and of 5 patients with nonallergic rhinitis. From one to four of these cells in the nasal epithelium and subepithelial layer of the 4 allergic patients were IgE-negative. In contrast, no IgE-negative cells existed in the deep layer of allergic nasal mucosae or in any nonallergic nasal mucosae. Our results suggest that mast cell progenitors, hematopoietic progenitor cells or multipotential blood cells exist in the allergic nasal mucosa, and may contribute to the increase of mast cells in the epithelium and subepithelial layer of allergic nasal mucosa.

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