Delayed Mortality of Radiation Chimeras: A Pathological and Hematological Study

Abstract

The hematological and pathological changes in lethally X-irradiated mice treated with isologous, homologous, or heterologous (rat) bone marrow are reported. Two different disease entities were observed in mice treated with homologous or heterologous bone marrow. Bone marrow aplasia chiefly occurred before the 30th day after irradiation. This resulted in death from septicemia or hemorrhage. The secondary bone marrow failure is explained by an immunological reaction of the host against the bone marrow graft. After the 30th postirradiation day, the animals were emaciated and had dermatitis, pneumonia, diarrhea caused by focal colitis with crypt degeneration, and necrosis of the liver. The delayed foreign bone marrow reaction is of a complex nature. Impaired recovery of radiation-induced lesions, decreased resistance to bacterial infections, probably due to generalized atrophy of the lymphatic tissues, as well as an immunological reaction of the graft against the host are postulated to be causal factors. An important difference was noted between animals treated with heterologous and those treated with homologous bone marrow. Bone marrow aplasia pre-dominated in the mice of the former group. In contrast, the mice of the latter group were chiefly affected by pneumonia, diarrhea, and colitis. Regeneration of the lymphatic tissues occurred within a month after irradiation in animals treated with isologous bone marrow, but it was retarded or failed to occur in animals treated with foreign bone marrow. The possible relation of the lymphatic-tissue changes to the etiology of the “secondary disease” is discussed.