Competitive repopulation in mice that underwent transplantation with GROβ_Δ4 and/or G-CSF mobilized PBMCs. (A) One-half million marrow cells from Boy J mice (CD45.1) were mixed with 1.0, 1.5, or 2 × 10⁶ PBMCs from C57BL/6 mice (CD45.2) mobilized with GROβ_Δ4 or G-CSF (ratio: 2:1, 3:1, and 4:1, respectively) and transplanted into lethally irradiated C57BL/6 mice. Donor and recipient chimerism in recipient blood was analyzed at 6 months after transplantation. The percentage of CD45.2 cells (PBMC-derived cells) is shown. The results are an average from 6 to 8 recipients. *P < .05 compared with G-CSF; †P < .05 compared with GROβ_Δ4, analyzed by ANOVA with Bonferroni correction. (B) Each individual chimeric mouse in panel A was killed and 10⁶ bone marrow cells transplanted in noncompetitive fashion into lethally irradiated C57BL6 mice. Chimerism in peripheral blood was analyzed and the percentage CD45.2 cells at 6 months after transplantation is shown. Data are the average of 3 to 6 mice with cells from each mouse transplanted into 2 recipients. *P < .05 compared with primary transplantation and G-CSF; †P < .05 compared with GROβ_Δ4 alone, analyzed by ANOVA with Bonferroni correction. (C) Marrow cells from the secondary recipients were transplanted in a similar manner and chimerism in peripheral blood was analyzed. *P < .05 compared with primary transplantation and G-CSF; †P < .05 compared with GROβ_Δ4 alone, analyzed by ANOVA with Bonferroni correction. Data are expressed as means (±SEM).