Reactive oxygen species (ROS) production is differentially upregulated between B6. Sle2c2 and B6 mice. B6.Sle2c2 mice present a higher percentage of GR1+ (A) and CD11b+ (B) splenocytes than B6. Bm12-chronic graft vs host disease (cGVHD) expands the GR1+ ROS+ in both strains, but eliminates the differences between strains. (C) At day (d)21 after cGVHD induction the ROS mean fluorescence intensity (MFI) was significantly higher in B6 GR1+ splenocytes than in B6.Sle2c2. (D) Time course analysis of ROS MFI in total peripheral blood leukocytes (PBLs) during cGVDH induction in mice treated with 12 × 2 human granulocyte-colony stimulation factor (huG-CSF). Means and standard error of the mean for five mice per group, with the significance value from the t-test are shown (*P < 0.05; ** P < 0.01). These data are representative of two sets of experiments.