Cultured (i.e., not exposed to gamma-retroviral supernatant) or transduced (i.e., exposed to supernatant) CD45.2+ lin- test cells were mixed with freshly-isolated CD45.1+ lin- competitor cells, and the mixtures were transplanted into 1100 cGy-conditioned Boy J hosts. In the left panel (A), 3 × 105 test cells were mixed with 3 × 105 competitor cells; in the right panel (B), 6 × 105 test cells were mixed with 2 × 105 competitor cells. Test cell chimerism is shown 4-5 months post-transplant from two independent experiments. N = 4 hosts for each parameter. *,P < 0.012 comparing fresh test cell chimerism to that of either cultured or transduced test cells. (Note: A portion of this data was published previously [2]).