Fetal liver repopulated 8.2 times as well as adult bone marrow in allogeneic fetal SCID recipients compared with 0.8 in nonirradiated allogeneic adult SCID recipients.

Donor fetal cell dose (× 10⁵) is shown on the x-axis. RUs in FL are shown on the y-axis. RUs are defined as the repopulating ability of 10⁵ BM cells, so RU per 10⁵ BM cells is always 1.0. RUs thus give a quantitative functional measure relative to the constant BM dose. The numbers of RU in FL over a range of FL doses are illustrated in fetal and adult recipients (recip) 6 weeks and 5 months after transplantation by using data from Table 2. RU in FL: RU FL/% FL = RU BM/% BM.