Peripheral blood cell counts. (A) Granulocytes. (B) T lymphocytes. (C) B lymphocytes. (D) Erythrocytes. Counts were taken in C57BL/6 mice following treatment with busulfan (2 × 10 mg/kg, days –1 and 0). Shown are mean values (± 1 SEM) for groups of 4 (untreated, ▪) and 5 (treated, □) mice. No significant difference of treated versus untreated mice (P > .05 using the Mann-Whitney U test) was observed for any of the cell counts except for CD3⁺ cells at the 16-day time point (*P = .03). Similarly, no statistically significant differences were observed for total leukocyte, hematocrit, hemoglobin, or platelet levels (data not shown).