Marrow-Thymus Interactions during Radiation Leukemogenesis in C57BL/Ka Mice¹

Transplantation of thymus and bone marrow cells from irradiated C57BL/Ka mice demonstrated the presence of potentially neoplastic cells in the thymus at 30 to 60 days postirradiation. During the same interval, no such cells could be detected in the bone marrow; moreover, the capacity of bone marrow cells to repopulate the thymus was impaired severely. These observations suggest that the primary site of neoplastic transformation in irradiated C57BL/Ka mice is the thymus rather than the bone marrow and that impaired thymic regeneration is a critical step in radiation leukemogenesis in mice.