Lin⁻c-kit^Lo and Lin⁻c-kit⁻ cells generate B-lineage cells in overnight culture. Lin⁻c-kit^Hi, Lin⁻c-kit^Lo, and Lin⁻c-kit⁻ cells were sorted from BM and placed in stromal cell free culture containing IL-7, FL, SCF, and stromal cell conditioned medium. Cells were harvested at days 1, 4, and 7. Costaining is shown for cells within lymphocyte light scatter and percentages of cells in each quadrant are given. C-kit^Hiand c-kit^Lo cultures were initiated with equal numbers of cells, but due to low frequency, half as many cells were used to initiate c-kit⁻ cultures. Representative data are shown from one of two independent experiments using pooled marrow from 10 mice.