Murine Hertwig's anemia: premature death after normal bone marrow transplantation is radiation dose-dependent

Marrow transplantation therapy in mice with heritable blood disorders usually leads to rapid blood cell normalization, but is sometimes followed by pancytopenia and premature death. This is especially true in mice with Hertwig's anemia (an/an). Unlike the +/+ recipients, 100% of whom survive for over a year, 66% of the mutant mice die by 6 months posttransplantation, and the rest die soon thereafter. It is not clear whether premature death is due to the radiation dose (10 Gy) or to the fact that the F1 mutant mice receive parental-type cells known to induce hybrid resistance. In the present report, experiments were designed to determine whether the F1-an/an host is more sensitive to radiation and/or resistant to continued expansion of the parental-type +/+ cells. The mutant mice are, indeed, more sensitive to irradiation, with an LD100/30 of 7 Gy as compared with an LD100/30 of 10 Gy for the +/+ mice. The times of anemia onset and death for mutant mice implanted with +/+ cells postirradiation is also radiation dose-dependent. Further evidence that death is due to host radiation damage rather than F1 hybrid resistance was provided by transplanting cells from three morbid 10 Gy-irradiation recipients into unirradiated, anemic, stem cell-deficient, F1-W/Wv secondary hosts. All recipients were repopulated by the original parental cells, were cured of their anemia, and survived for 52 weeks posttransplantation. The an/an mouse's heightened susceptibility to radiation damage appears to be the major factor in early death after transplantation therapy.