KINETICS AND QUANTITATION OF EOSINOPHIL AND NEUTROPHIL RECRUITMENT TOALLERGIC LUNG INFLAMMATION IN A BROWN-NORWAY RAT MODEL

We quantitated neutrophil and eosinophil migration into lung parenchym a using specific peroxidase enzyme assays, and into the bronchoalveola r compartment by bronchoalveolar lavage (BALF), in sensitized brown No rway (BN), Fischer, and Lewis rats and also assessed the lungs by hist opathology. Fourteen days after sensitization with ovalbumin (OA in al um [given subcutaneously] and OA with Bordetella pertussis [given intr aperitoneally]), rats were challenged with an OA aerosol for 1 h. In B N rats, there was marked perivascular and peribronchial edema, focal h emorrhages, and increase in lung wet weight and BALF protein content, accompanied by neutrophilic infiltration at 3-14 h postchallenge. Few eosinophils were seen at 14 h in lung tissue or in BALF. Neutrophils p ecked at 24 h in parenchyma ([94 +/- 7] x 10(6)) and in BALF ([2.7 +/- 0.4] x 10(6)) and declined rapidly thereafter. Marked eosinophil infi ltration into parenchyma was apparent by 24 h, Eosinophil accumulation peaked at 48 h in parenchyma ([127 +/- 18] x 10(6)) and at 72 h in BA LF ([10 +/- 2.4] x 10(6)), comprising up to 85% of lavage cells at thi s time. Lung eosinophilia persisted for at least 6 d with only a slow decline or clearance, not approximating baseline until day 13 after ch allenge. Histopathology showed peribronchial and interstitial eosinoph ilic pneumonia, most severe on day 3. In contrast to the BN rats, esse ntially no pulmonary inflammation was observed in Lewis and Fischer ra ts, This model in the BN rat, and the specific peroxidase assays for q uantitating tissue eosinophils and neutrophils, should be useful for i nvestigating the regulation of allergen-induced eosinophil and neutrop hil migration into and clearance from the lung.