Simulation results on strain differences. (A) Effect of the initial D2/B6 ratio. Data points represent the results (mean ± 1 SD) from 3 independent experiments. Data sets a and b used initially transplanted D2 proportions of 80% and 50% FL cells. Data set c (previously published26) used an initial D2 proportion of 20%. However, a different irradiation scheme as in the current study was used in this case. Solid lines represent corresponding average simulation results using identical parameter sets but different initial D2 proportions: a, 85%, b, 50%, and c, 30%. Goodness of fit measures, Δ, are as follows: a, 0.78; b, 0.89; and c, 0.92. (B) Reconstitution in nonchimeric situations. Black (D2) and gray (B6) dots represent mean leukocyte numbers (± 1 SEM) normalized to steady state counts of 6.7 × 10⁶for D2 and 7.4 × 10⁶for B6 mice (previously published33). The solid lines (black, D2; gray, B6) show average simulation results of reconstituting nonchimeric model systems starting from 20 initiating stem cells. Given is the fraction of normal steady state white blood cells in the mature leukocyte compartment of the simulation model using the D2 and the B6 parameter sets, respectively.