Functional equivalence of γ- and x-ray irradiation for long-term peripheral blood chimerism and acute myeloid leukemia transplant outcomes in mice.

Total body irradiation is routinely used for myeloablation before a mouse hematopoietic cell transplant. Widespread transition from 137Cs γ irradiators to x-ray systems has raised questions about whether these modalities yield equivalent biological outcomes. Although prior studies compared γ and x-ray irradiation in syngeneic transplants, their performance in reciprocal congenic models and in primary acute myeloid leukemia (AML) transplants remains unclear. Here, we systematically evaluated γ and x-ray irradiation across dose conditions and tested dose equivalents in CD45.1/CD45.2 reciprocal transplants and in AML transplant models. Although each modality exhibited distinct early effects, both ultimately supported comparable long-term donor peripheral blood (PB) chimerism in congenic transplants and equivalent AML engraftment, leukemic burden, and disease progression. These findings indicated that, with proper dose calibration, x-ray irradiation is a functionally effective alternative to γ irradiation for normal and malignant transplant studies.