A similarity and a difference between two models of late eosinophil accumulation into the airway induced by antigen exposure in actively sensitized brown Norway (BN) rats.

1. Exposure of sensitized Brown Norway (BN) rats to ovalbumin aerosol induced a remarkable and a sustained accumulation of eosinophils into broncho-alveolar lavage (BAL) fluid. 2. When male BN rats, sensitized by i.m. injection of ovalbumin and i.p. injection of killed Bordetella pertussis, were exposed to the antigen on day 14, eosinophils accumulated into BAL fluid, maximal 48 hr after antigen exposure. This accumulation of eosinophils was inhibited completely by administration of cyclosporin A (Cs A, 50 mg/kg/day) during induction phase, whereas it was inhibited slightly by administration of CsA (50 mg/kg) during the effector phase. 3. When BN rats were sensitized by weekly exposure of ovalbumin, eosinophils accumulated into BAL fluid, maximal 48 hr after the third exposure of antigen. The accumulation of eosinophils by this method was observed only in female rats and was inhibited completely by administration of CsA (50 mg/kg) during induction phase, whereas it was inhibited slightly by administration of CsA (50 mg/kg) during effector phase. 4. The present study demonstrates similarities and differences between two models of eosinophilia and also suggests increased function of T cells in BN rats.