THE ESSENTIAL ROLES OF PARENCHYMAL TISSUES AND PASSENGER LEUKOCYTES IN THE TOLERANCE INDUCED BY LIVER GRAFTING IN RATS

Liver allografts in pigs and rodents are uniquely capable of inducing tolerance to themselves and to other grafts of donor tissues, instead of succumbing to the acute rejection that follows transplantation of o ther allogeneic tissues. We demonstrate here, using normal and chimaer ic rat liver grafts, that both the allogeneic liver parenchyma and the intrahepatic leukocytes of donor type contribute to the establishment of long-term tolerance, each component being essential and complement ary. The essential role of hepatic parenchyma may be related to its co ntinuous release of soluble transplantation antigens that facilitate t olerogenesis. We suggest that clinical attempts at tolerance induction by the infusion of donor bone marrow-derived leukocytes may likewise be facilitated by the coadministration of soluble transplantation anti gens of donor type.