Kinetics of appearance of different types of human hematopoietic cells in NOD/SCID mice transplanted with 10⁷low-density human fetal liver cells. Values shown represent the numbers calculated to be present in each entire mouse, assuming 2 femurs and 2 tibias comprise 25% of this value.60 Results from 2 independent experiments have been pooled (2 to 6 mice per time point). Previously published data for grafts of 10⁷ light-density human cord blood cells (dashed line)42 or 2 × 10⁷ light-density human adult marrow cells (dotted line)48 are shown for comparison.