The average number of transduced stem/progenitor clones contributing to blood cell production. (A) Animal 96E019 granulocytes. (B) Animal 96E025 granulocytes. (C) Animal 96E025 mononuclear cells (> 95% lymphocytes). Arrows indicate the time of 3 Gy TBI. P values are determined by comparing the time point immediately before 3 Gy TBI with subsequent time points after 3 Gy TBI as shown. The clone number refers to the average number of clones from 3 independent LAM-PCRs consisting of 6 replicates. (A) In animal 96E019, the clone numbers immediately after TBI were decreased significantly (P < .05), and the recovery from the lowest value after TBI to the last follow-up was significantly increased (P < .01). (B) In the animal 96E025, the immediate decrease was more severe (P < .001) and clonal fluctuation has persisted for the entire follow-up period. There was at least a partial recovery in clonal diversity (P < .05) by 14 months after 3 Gy TBI. (C) Lymphocyte fraction (mononuclear cell [MNC]) from animal 96E025 did not show any significant changes in clonal numbers (P = not significant [ns]) after 3 Gy low-dose TBI despite the significant impact on clonal derivation of granulocytes as shown in panel B. Error bars represent standard deviation.