IMPORTANCE OF ISCHEMIA-REPERFUSION LESIONS: After transplantation, ischemia-reperfusion lesions are associated with an increased risk of acute rejection, late recovery of liver function, or chronic graft dysfunction. In all, about 20% of the grafts are lost. The importance of prevention is evident. HEME-OXYGENASE: It has been shown that heme-oxygenase, an anti-oxidant reducing apoptosis, reduces the extent of ischemia-reperfusion lesions after liver, heart, kidney or Langerhans islet transplantation. OTHER COMPOUNDS WITH INTERESTING PROPERTIES: Other compounds also have interesting properties for preventing ischemia-reperfusion lesions: a specific metallo-protease inhibitor, L-arginine, a selective agonist of the PGE1 receptor, estrogens, low-dose cyclosporine, and certain immunosuppressors (FTY 720, anti CD28, anti B7-1), and rPSGL-Ig ligand.