Improved survival of dogs exposed to fission neutron irradiation and transplanted with DLA identical bone marrow.

The survival of dogs exposed to fission neutron irradiation, a component in the radiation dose of reactor accidents, was improved by the administration of DLA-identical allogeneic bone marrow but not by the administration of DLA-mismatched allogeneic bone marrow. The level of survival observed at 2.55 Gy was similar to that observed after autologous bone marrow transplantation. The transplanted allogeneic bone marrow, however, survived for only 2-3 weeks, but provided enough mature peripheral blood cells during this time to endure the initial radiation insult. Subsequent recovery of autologous bone marrow led to the ultimate survival of the dogs. Additional radiation protocols were evaluated in order to obtain permanent engraftment of the donor marrow cells. A higher neutron dose or a second radiation of 6.0 Gy gamma rays led to severe damage of the gastrointestinal tract and an early death. A third regimen, a second radiation dose of 4.0 Gy of gamma rays, led to permanent engraftment in one dog but its survival was complicated by graft-versus-host disease.