Early detection of apoptosis and Fas ligand expression in hepatic graft-versus-host disease after rat small bowel transplantation

Background. The liver is one of the primary targets of acute graft-versus-h ost disease (GVHD), which is the principal complication that occurs after a llogeneic intestinal transplantation. The purpose of this study is to inves tigate the involvement of the Fas/Fas ligand system in hepatic GVHD after r at semiallogeneic intestinal transplantation. Materials and methods. Liver samples were serially harvested from LEW x BN F-1 (LBNF1) recipients of either LEW heterotopic intestinal allografts (gro up 1) or LBNF1 isografts (group 2), on Days 1, 3, 5, 9, and 13 posttranspla nt. Results. In group 1, hepatic injuries as assessed by either serum aspartate aminotransferase (AST) level, alanine aminotransferase (ALT) level, or cel lular infiltration on HE staining became apparent after Day 13. The inciden ce of apoptosis, examined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end-labeling (TUNEL), was observed to steadily increase i n the liver from Day 5 accompanied by a progression of GVHD: 17.5 +/- 3.1 a nd 3.1 +/- 0.4 cells/held (200x) in groups 1 and 2, respectively. In an imm unohistochemical study, Fas was constitutively expressed in the liver in bo th groups, while Fas ligand was expressed most extensively on Day 13 in gro up 1. Immunoreactivity of both Fas and Fas ligand was observed in hepatocyt es, in addition to leukocytes. Analysis by reverse transcription polymerase chain reaction also revealed the expression of Fas mRNA 60 be constitutive in both groups, while that of Fas ligand mRNA increased significantly from Day 5 and peaked on Day 13 in group 1, and the expression was 10 times str onger than that for isogeneic combination (group 2). Conclusion. Early detection of upregulated Fas ligand and increased apoptos is is thus considered to be potentially a useful tool for the diagnosis of hepatic GVHD. (C) 1999 Academic Press.