Effects of HOXB4 overexpression on the number of myeloid and pre-B colony-forming cells after BMT. Results shown are the means ± SD of the numbers of in vitro myeloid colony-forming cells in bone marrow (top) and spleen (middle) and of IL-7–responsive B-lymphoid progenitor cells (pre-B CFC) in the bone marrow (bottom) of individual neo (▨) and HOXB4 (▪) mice at various time points after transplantation. The number of neo andHOXB4 mice analyzed at each time point are shown in Fig 1B. Consistent with their preferential derivation fromHOXB4-transduced cells, a major proportion of myeloid and pre-B lymphoid progenitor cells in HOXB4 mice were G418-resistant (HOXB4 mice, 59% ± 9% v neo mice, 37% ± 10% for all 3 experiments).