Intratracheal but not intraperitoneal or intravenous rmTNF-α induced hepatocytotoxicity and elevated serum TNF-α in TRAF1−/− mice. Serum harvested from WT and TRAF1−/− mice 20 hours after treatment with rmTNF-α (5 μg/mouse) either intratracheally (IT), intravenously (IV, tail vein), or intraperitoneally (IP) were assayed for ALT (A), AST (B), or murine TNF-α (C), as described in Materials and Methods. Mean ± SEM, n = 3 to 5. *, P < 0.01 intratracheal TNF-α treatment of TRAF1−/− as compared to all other values.