VIRUS-INDUCED INCREASES IN AIRWAY MAST-CELLS IN BROWN-NORWAY RATS AREASSOCIATED WITH ENHANCED PULMONARY VIRAL REPLICATION AND PERSISTING LYMPHOCYTIC INFILTRATION

Brown Norway (BN) rats are more susceptible than Fischer 344 (F344) ra ts to parainfluenza virus-induced lung injury and to bronchiolar mast cell increases that are associated with persistent airway hyperrespons iveness. In this study, pulmonary viral replication as well as immune, inflammatory, and airway mast cell responses to Sendai virus infectio n were compared between neonatal BN and F344 rats. BN rats supported p rolonged viral replication, and viral titers in BN rats were 5-fold hi gher (p<.05) than in F344 rats at 7 days after inoculation. F344 rats had 18-fold higher (p<.06) numbers of lymphocytes in bronchoalveolar l avage fluid at 7 days after inoculation than did BN rats. Persisting b ronchiolar aggregates of lymphocytes, plasma cells, and macrophages we re more common, and increases in bronchiolar mast cells were greater i n BN rats than in F344 rats. No strain differences were detected in br onchiolar intramural infiltrates of CD4+ or CD8+ cells. The greater su sceptibility of BN rats to virus-induced increases in bronchiolar mast cells and airway responsiveness may be the result of their less effic ient viral clearance mechanisms and more persistent bronchiole-centere d inflammatory response.