DERMATOPHAGOIDES-FARINAE-INDUCED PULMONARY EOSINOPHILIC INFLAMMATION IN MICE

Dermatophagoines farinae (Der f) is one of the most common species of dust mites that induce asthma and allergic rhinitis. We have reported that Der f challenge on sensitized mice elicited a distinct type of hy persensitivity, called early-type hypersensitivity (ETH), in subcutane ous tissues and in airways. The airway ETH was accompanied by a series of inflammatory and immunological events including cytokine productio n, adhesion molecule expression, inflammatory cell infiltration eosino philia, and airway hyperreactivity. In the present study, we further d efined the course of the Der-f-induced eosinophilia and examined the l ocal cytokine gene expression and the roles of cytokines, mast-cell-de rived vasoactive amines, and corticosteroids in the development of pul monary eosinophilia. BALB/c mice were sensitized with crude extract of Der fin complete Freund's adjuvant and were intranasally challenged w ith Der fon day 14 after sensitization. The number of blood eosinophil s, total and differential leukocyte counts in bronchoalveolar lavage ( BAL) fluids, and the expression of cytokine genes in BAL cells were as sessed at various time points after challenge for up to 12 days. The t otal number of leukocytes in the BAL fluids was increased 6 h after ch allenge (AC) and peaked at 72 h. The early cellular response in the BA L fluids was dominated by neutrophils which were subsequently replaced by a marked infiltration of eosinophils. The number of eosinophils in BAL fluids increased at 24 h and peaked at 72 h, making up 43% of all cells recovered by BAL. BAL eosinophils declined gradually to normal background levels around day 12. Concurrently, there was a significant reduction in the number of eosinophils in blood 24 h AC. The number o f blood eosinophils increased thereafter, reached a peak at 72 h, and remained above baseline level for up to 10 days. Saline challenge did not induce eosinophilia in BAL fluids and blood of sensitized mice. Hi stopathological examination revealed a mixed granulocytic, monocytic p ulmonary inflammation with a large number of eosinophils accumulating within the submucosa of the airways and blood Vessels of sensitized mi ce after challenge. Der f challenge induced a sequential expression pa ttern of eight cytokine genes in BAL cells. The mRNA of interleukin (I L)-1 beta and tumor necrosis factor (TNF)-alpha strongly expressed thr oughout the course of the experiment. The IL-6 mRNA expression peaked at 0.5-72 h, IL-10 at 1-6 and 48-72 h, IL-4 at 6-72 h, IL-2 at 6-96 h, IL-5 at 24-72 h, and interferon-gamma at 24-96 h. Intraperitoneal inj ection of sensitized mice with monoclonal antibody (mAb) to murine IL- 5 (TRFK5, 300 mu g/mouse) Ih before challenge caused 62% suppression o f eosinophils in the BAL fluids. The concomitant accumulation of neutr ophils and mononuclear cells, however, was not affected by this treatm ent. On the other hand. intranasal administration of mAb to murine TNF -alpha (MP6-XT3, 20 mu g/mouse), but not IL-5, 1 h before challenge an d 24 h AC significantly reduced the numbers of eosinophils, neutrophil s, and lymphocytes in the BAL fluids. The intraperitoneal injection of dexamethasone (50 mg/kg) for a total of four times resulted in total inhibition of the Der-f-induced cellular responses, whereas Vasoactive amine antagonists (diphenhydramine, ketanserin and cyprohepatidine) d id not show any effect.