DIAGN MICROBIOL INFECT DIS 397 1990;13:397-404 The Pattern of Lung Injury Induced After Pulmonary Exposure to Tumor Necrosis Factor- Depends on the Route of Administration Henry J. Fuchs, Robert Debs, John S. Patton, and H. Denny Liggitt INTRODUCTION Tumor necrosis factor-cx (TNF-o0 has been implicated in the pathogenesis of the sepsis syndrome (Tracey et al., 1986). TNF-o~ is secreted by mononuclear phagocytes after proper stimulation in vitro. Bacte- rial lipopolysaccharide (LPS) is one important stim- ulus of TNF-~x synthesis (Beutler and Cerami, 1986). In fact, infusion of LPS into humans results in the appearance of TNF-cx in blood (Michie et al., 1988). Because passive immunization against TNF-0t, be- fore administration of LPS, significantly reduces mortality in mice (Beutler et al., 1985) and physio- logic abnormalities in primates (Tracey et al., 1987), TNF-cx is thought to participate directly in the organ injury that occurs during sepsis syndrome. The lung is an important target organ for injury during the sepsis syndrome. The histologic hall- marks of lung injury associated with sepsis include alveolar capillary endothelial injury, which results in alveolar epithelial injury, alveolar exudation, and alveolar and interstitial neutrophil accumulations (Brigham and Meyrick, 1986). Intravenous admin- istration of large amounts of TNF-o~ injures pulmo- nary arterioles, venules, and capillaries. This results From the Department of Pharmacological Sciences (HJ.F., J.S.P., H.D.L.), Genentech, Inc., South San Francisco; and Cancer Research Institute (R.D.), University of California, San Francisco, California. Present address (H.D.L.): Department of Comparative Med- icine, School of Medicine, University of Washington, Seattle. Address reprints requests to: Henry J. Fuchs, M.D., Depart- ment of Immunobiology, 460 Point San Bruno Boulevard, South San Francisco, CA 94080. Received May 10, 1990; revised and accepted June 10, 1990. © 1990 Elsevier Science Publishing Co. 655 Avenue of the Americas, New York, NY 10010 0732-8893/90/$3.50 in alveolar epithelial injury, alveolar exudation, al- veolar neutrophil accumulations, and capillary en- dothelial cell injury (Goldblum et al., 1989). It has recently been shown that intravenous administra- tion of large amounts of TNF-e~ to rats induces pul- monary edema and mechanical changes identical to that seen in the adult respiratory distress syndrome (Ferrari-Baliviera et al., 1989) Therefore, TNF-oLelab- orated on the blood side of the alveolar--capillary barrier may be responsible for a major portion of lung injury. Phagocytes on the air side of the alveolar-capil- lary barrier are an important source of production of TNF-cx and may contribute to the pathogenesis of organ injury during sepsis. Alveolar macrophages are the major mononuclear phagocytes in the lung (Brain, 1985) and constitute an important defense mechanism against inhaled bacteria (Green and Kass, 1964). Pulmonary administration of LPS results in the release of TNF-~ by alveolar macrophages and is accompanied by alveolar epithelial injury and ac- cumulation of neutrophils (Nelson et al., 1989). The direct effects of TNF-o~on the respiratory epithelium are not known. In the present investigation, we ex- amined whether direct application of TNF-a to the alveolar epithelial surface would produce histologic changes similar to that seen following intravenous administration. MATERIALS AND METHODS Materials Recombinant human TNF-c~ was expressed in Esch- erichia coli, purified, and stored frozen at -70°C