The role of prothymocytes in radiation-induced leukemogenesis in C57BL/Rij mice.
Following transplantation of bone marrow into recipient mice subjected to irradiation with four weekly fractions of 1.8 Gy, donor progenitor cells were found to compete with host elements for colonization of the thymus. The capacity for thymus repopulation of bone marrow cells from 4 X 1.8 Gy irradiated mice is decreased to a similar low level as that of regenerating bone marrow derived from lethally irradiated mice reconstituted with isogeneic marrow. It was calculated that the prothymocyte content of both types of regenerating marrow was less than 0.1% of that of normal marrow. Long-term cultures of C57BL bone marrow were found to contain the same numbers of prothymocytes per CFU-S as normal bone marrow, in contrast to cultured marrow from (C3H X AKR)F1 mice, that shows a striking decrease of prothymocytes. Normal bone marrow cells and long-term cultured bone marrow cells of C57BL mice were about equally effective on the basis of numbers of CFU-S injected in protecting 4 X 1.8 Gy irradiated syngeneic recipients from developing thymic lymphomas, while regenerating bone marrow was virtually nonprotective. These data are interpreted as supporting the notion that prothymocytes from the bone marrow play a crucial role in the prevention of radiation-induced thymic lymphomas.
D000818:Animals; D016026:Bone Marrow Transplantation; D003114:Colony-Forming Units Assay; D006412:Hematopoietic Stem Cells / Q000502:physiology; D007953:Leukemia, Radiation-Induced / Q000503:physiopathology* / Q000628:therapy; D008214:Lymphocytes / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D013950:Thymus Gland / Q000503:physiopathology* / Q000528:radiation effects