Evidence of the alloimmunogenic potential of donor periodontal ligament

The alloimmunogenic potential of each of the tooth graft components (periodontal ligament, mineralized root surface and passenger leukocytes) was evaluated. The model employed was orthotopic tooth allografts in inbred strains of Syrian hamsters. Isolated allogenic mineralized root surface is not immunogenic, as was demonstrated by the inability of tooth grafts to stimulate accelerated rejection of a subsequent skin graft if the tooth had undergone pretransplant enzymolysis of its periodontal ligament. Similarly, tooth grafts were rendered nonimmunogenic if exposed to repeated freezing and thawing. In contrast, isolated allogenic periodontal ligament on a syngeneic tooth graft was shown to evoke an accelerated rejection of skin grafts. Thus, the normal median survival time of skin (11.3 days) in the strain combination of hamsters employed was reduced to 7.4 days following exposure to an orthotopic tooth graft in which the periodontal ligament was the only obvious source of alloantigen. Prior elimination of a tooth allograft's passenger leukocytes by lethal whole body gamma-irradiation did not affect the graft's ability to sensitize the host.