Production of hematopoietic cells, CFU-GMs, and BFU-Es by wild-type and IL-6^-/- LTBMCs. Cultures were established and maintained as in Figure 1. Total hematopoietic cells (A), CFU-GMs (B), and BFU-Es (C) in culture medium and in the stromal layer were evaluated at weekly intervals. Results are expressed as the mean ± standard deviation (SD) of 4 experiments. ^*P < .01, for wild-type versus IL-6^-/- cultures.