IMMUNOPATHOLOGICAL OBSERVATIONS AFTER XENOGENEIC LIVER PERFUSIONS USING DONOR PIGS TRANSGENIC FOR HUMAN DECAY-ACCELERATING FACTOR

Background, Donor pigs transgenic for human decay-accelerating factor (hDAF) were used in a xenogeneic ex vivo liver perfusion model to stud y the effect of this modification on the development of hyperacute rej ection, Methods. Three transgenic pigs were hepatectomized after hypot hermic portal and transaortal gravity perfusion, Livers from six nontr ansgenic pigs served as controls, All livers were perfused for 3 hr wi th human blood from two donors diluted to a hematocrit of 30%, Particu lar importance was placed on the use of an optimal perfusion technique incorporating the floating suspension of the organs in a waterbath an d intermittent external pressurization. Biochemical, physiological, an d immunological parameters were assessed. Tissue specimens taken befor e and after perfusion were analyzed using routine histology, electron microscopy, and immunohistology, Results, Complement activation was mo re pronounced in the control group, AP50 and CH50 values fell to about 60% of the initial levels in control experiments, whereas they remain ed at 80% of the initial levels during perfusion of hDAF livers, After 180 min, pig tumor necrosis factor a levels were 7862+/-1645 pg/ml fo r unmodified livers and 2830+/-734 pg/ml in the hDAF group, Human tumo r necrosis factor alpha levels were similar in both groups, Control li vers showed marked morphological alterations and distinct deposition o f complement factors, whereas livers expressing hDAF showed no signs o f hepatocellular necrosis and almost no complement deposition beyond C 3 activation. Conclusions, These results confirm that the transgenic e xpression of the human complement regulatory protein hDAF reduces comp lement activation and prevents hyperacute rejection in a xenogeneic li ver perfusion model over the 3-hr evaluation period used in this study .