Experimental granulomatous alveolitis in rat. Effect of antigen manipulation, smoke exposure and route of administration.

When Sephadex beads (0.45mg/kg b.w) are instilled intratracheally into rats, a granulomatous alveolitis with giant cell formation and fibrosis occurs. Moreover, the events in the alveolar region are paralleled by an eosinophil-dominated peribronchitis/bronchiolitis and perivasculitis. Bronchoalveolar lavage (BAL) shows a very distinct feature with an early pronounced neutrophil increase, followed by an increase of eosinophils and lymphocytes. BAL findings returned to normal after 1-2 weeks, but tissue morphology showed persistent inflammation with large numbers of eosinophils and to a lesser degree mononuclear cells, peribronchially and perivascularly several weeks after the instillation. Fragmentation of the Sephadex beads by ultrasonication dramatically diminished the response, giving a transient neutrophil alveolitis, without eosinophils and with no granuloma formation. On the other hand, when the Sephadex dose was divided into three, given 10 days apart, a more pronounced fibrosing activity occurred, with mast cells appearing in the collagen rich granulomas. Finally, smoke exposure had a significant suppressive effect upon the response. The numbers of cells in the interstitium as well as in the peribronchial and perivascular tissue were markedly decreased in the smoke exposed group compared to the controls. This decrease was mainly due to decreased numbers of mononuclear cells, while the numbers of eosinophils remained unchanged.