Background: In allergic rhinitis, metachromatic cells in the nasal epithelium increase in number and are thought to play an important role in nasal allergic manifestation.
Methods: To determine immunohistochemical and functional characteristics of the metachromatic cells, nasal scrapings and their dispersed cells from patients with perennial allergic rhinitis were studied.
Results: Eighty-three percent of all metachromatic cells in dispersed cell preparations were tryptase-positive mast cells (MCT), 10% were tryptase-chymase-positive cells (MCTC), and 7% were negative (n = 10). The mean histamine chymase-positive cells (MCTC), and 7% were negative (n = 10). The mean histamine content per metachromatic cell was 1.9 +/- 2 pg. The histamine content and histamine release from nasal surface scrapings of patients sensitized with mite antigen were strongly correlated with the level of serum IgE antibody for mite antigen. The net histamine release from nasal scraping was antigen-dose-dependent (1:2 x 10(7) to 1:2 x 10(3) dilution), and the antigen stimulated release of up to 17% of cell-associated histamine within 5 to 7 minutes. Histamine release from nasal scrapings induced by calcium ionophore A23187 was up to 21% of cell-associated histamine within 2 to 4 minutes, but no histamine release was stimulated by compound 48/80, substance P, or poly-L-lysine. Histamine release from nasal scrapings was inhibited 46% (10(-5) mol/L) to 96% (10(-4) mol/L) by quercetin and 58% (10(-4) mol/L) to 72% (10(-3) mol/L) by sodium cromoglycate.
Conclusions: These findings show the predominant characteristics of mast cells in the nasal epithelium in allergic rhinitis, and this information may be useful in relation to a therapeutic approach.