EFFECT OF ALLERGEN IMMUNOTHERAPY ON NASAL RESPONSES IN GUINEA-PIGS WITH ALLERGIC RHINITIS

Methods We have investigated the effects of allergen immunotherapy on the nasal responses in the guinea-pigs with allergic rhinitis. Thirty- three male Hartley guinea-pigs with allergic rhinitis were divided int o three groups; those receiving intradermal injection of saline (Group 1) or 0.1% ovalbumin (Group 2) 6 days after the last intranasal sensi tization, and those injected with 0.1% ovalbumin intradermally once da ily for 6 consecutive days from the next day after the last intranasal sensitization (Group 3). Results The dye leakage and histamine conten t into the nasal lavage significantly decreased at 30 min after antige n challenge in Group 3, compared with Group 1 or 2. We also observed t he change of mast cell numbers in superficial nasal mucosa, lamina pro pria and injected dorsal skin. The number of mast cells in superficial nasal mucosa significantly decreased in Group 3 compared with Group 1 or 2, but not those in nasal lamina propria or dorsal skin. Conclusio ns These results suggest that the improvements of nasal responses such as dye leakage and histamine content may be caused by the decrease of mast cell numbers in the superficial mucosal layer after the specific immunotherapy, which may be developing tolerance and one of the mecha nisms underlying the beneficial effect of immunotherapy.