Level of Flt3-ligand in plasma: a possible new bio-indicator for radiation-induced aplasia

Purpose: To follow plasma Flt3-ligand (FL) concentrations in irradiated animals in order to evaluate it as an indicator of bone marrow damage for the management of accidental radiation-induced aplasia. Materials and methods: Non-human primates were irradiated at doses ranging from 2 to 8 Gy, using whole- or partial-body irradiation. Plasma FL concentrations and blood cell counts were determined daily. Results: FL concentrations increased as early as day 2 after irradiation, whatever the irradiation dose. Increase in plasma FL concentration on day 5 post-irradiation was correlated with radiation dose and with the severity of radiation-induced aplasia. During the course of aplasia, FL concentrations in plasma were inversely correlated with neutrophil counts. A peak in FL concentration appeared before the neutrophil nadir, and the subsequent decrease in FL concentration was correlated with the recovery of blood-cell populations. Conclusions : Monitoring plasma FL concentration can be used as an indicator of radiation-induced marrow aplasia, and this may be of use in accidental irradiation situations.