Host Sex-Dependent Growth of Potential Thy-1⁺ Lymphoma Cells That Appear in the Thymus of X-Irradiated NFS Mice

During the course of studies designed to detect potentially leukemic cells in radiation lymphomagenesis, using an opposite-sex (male → female) transplantation assay method, we previously found that potential <tex-math>${\rm Thy}\text{-}1^{-}$</tex-math> lymphoma cells are generated in the bone marrow of NFS mice exposed to a split-dose irradiation (1.7 Gy × 4), while potential Thy-1⁺ lymphoma cells are not detectable. In this report, using a (female → male) intrathymic transplantation assay system we show that potential Thy-1⁺ lymphoma cells were generated in the thymus of female NFS mice exposed to split-dose irradiation, and reconfirm that such cells were not detected in the (male → female) transplantation system. These results demonstrate that the detection of potential Thy-1⁺ lymphoma cells strictly depends on the transplantation system.