In vivo limiting dilution analysis of repopulating cells.

A group of irradiated mice were transplanted with varying numbers of fetal liver cells at day 12 (A) and day 16 (B) of gestation. At 4 and 20 weeks after transplantation peripheral blood cells were analyzed for the presence of fetal liver-derived cells. The number of recipients that survived until the time of analysis were 6 to 13 mice and 8 to 13 mice per group for day 12 and day 16 fetal liver cell transplantation. Mice that did not contain more than 1% of fetal liver-derived cells in a total of fetal liver- and competitor-derived cells were considered to be negative.