Detection of hematogones after allogeneic HSCT. (A) Typical appearance of hematogones in the bone marrow after HSCT (Giemsa staining ×1000; OLYMPUS BH-2 microscope [Olympus]; ACT-2U imaging software [Nikon]; 27°C). (B) Evaluation of hematogones on a 5-color FACS. Hematogones are defined as MNCs coexpressing CD10 and CD19 in the bone marrow at engraftment. They include CD34⁺CD38⁺CD10⁺CD19⁺Lin⁻ pro-B cells, CD34^−/loCD38⁺CD10⁺CD19⁺ pre-B cells, and CD34⁻CD38⁺CD10⁺CD19⁺CD20⁺ immature B cells. (C) Percentage of hematogones in the bone marrow MNCs in patients who received BMT and CBT. CBT recipients presented much higher frequency of hematogones compared with BMT recipients (P < .001). Solid bars indicate the median percentage of hematogones for each recipient; MNC, mononuclear cells; BMT, bone marrow transplantation; and CBT, cord blood transplantation. (D) The relationship between the day of engraftment and percentages of hematogones. There was no relationship between these parameters. (E) IGH rearrangement analysis of purified hematogones. B-cell precursors were polyclonal in all 106 recipients analyzed.