Flow cytometric analysis of donor-type cells in the blood of BALB/c hosts receiving C57BL/Ka low-density blood mononuclear cells. Donors were treated with G-CSF, and host blood cells were examined more than 160 days after the injection of donor cells. Host mononuclear cells were stained with FITC-conjugated anti–H-2^b antibodies and PE-conjugated anti-Thy 1.2, anti–Mac-1 and anti–Gr-1, or anti-B220 antibodies (B, C, and D, respectively). Control staining is shown in (A). Boxes enclose donor-type T cells, macrophages and granulocytes, or B cells. The mean percentage of donor type cells in each category is summarized for groups of three mice receiving three different dosages of cells.