title: Spontaneous long-term acceptance of RT-1-incompatible liver allografts in inbred rats. Analysis of the immune status.
abstract: In several combinations of inbred rats, liver allografts are spontaneously tolerated, and after a few weeks liver tolerant rats are in a state of donor-specific transplantation tolerance. In vivo and in vitro experiments were conducted to analyze the immunological status of LEW or BN rats with spontaneously tolerated (LEW X BN) F1 liver allografts several months after transplantation. Acute rejection of secondary donor-specific heart allografts retransplanted from liver-tolerant rats to normal syngeneic hosts suggests that the state of tolerance in liver-tolerant rats is related to an active modification of the immune system of the rat and not to a reduced immunogenicity of the graft. No cytotoxic antibodies or cells were found in liver-tolerant rats. Reactivity in mixed lymphocyte culture was normal or slightly reduced. Arguments for the presence of splenic suppressor cells were found in LEW tolerant rats using a local graft-versus-host assay, but these could not be found in BN rats, or when attempting to transfer or to break the tolerance state. A nonspecific humoral blocking factor was found in vitro in liver-tolerant rats but transfer of serum from liver-tolerant rats to normal syngeneic hosts did not permit a significant prolongation of donor-specific heart allografts. These results suggest that more than one mechanism may be involved at the maintenance phase of liver allograft tolerance.
mesh_terms: D000818:Animals; D006087:Graft vs Host Reaction; D007108:Immune Tolerance; D016031:Liver Transplantation; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains / Q000276:immunology*; D013997:Time Factors; D014181:Transplantation Immunology; D014184:Transplantation, Homologous