Tissue distribution of in utero transplanted cells. The PB, BM, and spleen of fetal recipients of Ly5.1 lineage-depleted progenitors were analyzed for the presence of donor cells 4 weeks after in utero injection. Mice with ≥1% Ly5.1 donor cells were considered chimeric. The percentage of total Ly5⁺ cells that expressed the Ly5.1 donor marker is shown for individual chimeric mice.The horizontal bar indicates the mean percentage of donor cells in each group.