Acute lung injury was studied in rats by instMation ef cationic BSA, native BSA and saline. Rats instilled with cationic BSA developed a seve re acute alveolar hemerrhage, accompanied by fibrinoid deposits, massive accumulation of platelets in the alveolar cap{llaries aHd severe darnage of the epithelial cells. Preimmunization with BSA promoted an enhancement oi tissue injury, Similar changes of a lesser degree were also obseryed in rats preimmunized with BSA and instilled with native BSA, but

more »

... ot in rats svhich had not been preimmunized. Furthermore, linear deposits of BSA and rat IgG along the alveolar wall basement rnembrane were observed in rats presensitized with BSA and instilled with catienic BSA. These results suggest that the binding of cationic antigens to the anionic sites and the "in situ" formation of IC in the alveolar structures may be important in modulating lung injury.