In vivo MMC sensitivity of BM LTC-IC cells fromFac +/+ and Fac −/− mice. (A) The number of CFC from 5-week LTBMC established 2 and 6 days after 1 single MMC (0.75 mg/kg) injection. (B) The number of CFC from 5-week LTBMC established 1, 3, and 5 weeks after repeated MMC injection of 0.3 mg/kg. Controls represent saline-injected mice. Data represent the mean ± SEM of triplicate determinations from 2 mice. Significant differences between controls and MMC-injected mice (*P < .01; **P < .05; #P < .005; ##P < .0005). The absence of SEM bars represents values too low to appear in the graph.