Figure 4.

In vivo administration of TGF-β₁ or SDF-1 enhances the ability of human HSCs in regenerating primary NOD/SCID mice to engraft secondary mice. Equal aliquots of primary mouse marrow cells were transplanted into secondary mice (.25 primary mouse marrow equivalents per secondary mouse) and 6 to 8 wk later the number of different types of human cells in the four hind leg bones of each mouse was determined. These were used to identify mice as positive or negative for human multilineage engraftment and thence to provide data for HSC calculations. Each bar indicates the mean ± SEM of the total number of HSCs determined to be present in the control (gray bar) primary mice or in the primary mice infected with SDF-1 or TGF-β₁ and assessed wither 1 d (black bars) or 3 d (white bars) after the last infection.