Limiting dilution analysis of L-selectin^Neg progenitor lineage potential after intravenous transplantation. L-selectin^Neg progenitors were collected and transplanted intravenously into radiation-conditioned hosts as described for Figure 2 with doses transplanted per mouse ranging from 5 to 160 cells. From 3 to 13 mice were given transplants at each dose (70 mice total) over 4 replicate experiments. Engraftment was assessed between 27 and 29 days after transplantation by analyzing host tissues for donor-derived cells in specific lineages. Horizontal bars mark the 37% negative engraftment point predicting active progenitor frequencies, which are shown by vertical bars and dose numbers along the x-axis. Correlation coefficients (r) are given for each curve extrapolated from the data. Thymic T cells, □; splenic T cells, ▪; splenic B cells, (○); marrow B cells, (•); marrow myeloid cells, (▵).