Figure 4.

sFasL is not active in vivo. (A) BALB/c mice (female, 8 wk old) were injected intravenously with sFasL or sTRAIL (12.5 μg). Within 10 min, anti-Flag antibodies (50 μg) or control IgG₁ (Ctrl) antibodies (50 μg) were injected using the same route of administration. Mice receiving sFasL and anti-Flag antibodies (four mice) died within 3 h (mean survival: 2.25 ± 0.5 h). Injection of sFasL alone (four mice), sFasL followed by control IgG₁ (two mice), anti-Flag alone (two mice), sTRAIL alone (four mice), or sTRAIL plus anti-Flag antibody (four mice) did not lead to death or to any sign of sickness of the animals. (B) Hepatic injury of mice treated with sFasL in the presence of anti-Flag antibodies or of a murine control antibody (IgG₁). 24 h later (sFasL + control antibodies) or immediately after death (sFasL + anti-Flag antibodies), livers were fixed with 4% formaldehyde and embedded in paraffin. Sections were either stained with hematoxylin and eosin, or used for in situ DNA end labeling using the terminal uridyl transferase nicked ends labeling (TUNEL) method. Normal liver tissue is seen in a, whereas hepatocytes with pyknotic and fragmented nuclei are surrounded by red blood cells in b. In situ DNA end labeling confirms apoptotic cell death in d.