FL enhances the yield of LTCIC in stroma-free culture. CD34⁺ CD38^dim cells and CD34⁺ CD38^dim CD33^dim HLA-DR⁺ cells were cultured with [IL-3 + IL-6 + KL] ± FL for 14 to 19 days and analyzed for CFU-GM and LTCIC. This figure shows the fold change in LTCIC number relative to input. In trials 7 and 8, low sort yields did not permit the establishment of cultures without FL. Cell sources: trials 1 and 2, normal bone marrow; trials 3 through 8, mobilized blood. Average CFU-GM expansions: 481- ± 169-fold with FL; 74- ± 34-fold without FL. Error bars show 95% confidence intervals; bars on trials 1, 3, and 8 are too short to be visible. Significance of difference for (▪) +FL versus (□) −FL in individual trials: *P < .05; **P < .02; ***P < .0004.