Effect of time and dose of 5-FU exposure on various BM MNC populations. BM MNCs from 10 donor samples were exposed to various doses of 5-FU for 0.5, 2, and 24 hours at 37 °C. The mean (±SEM) percentages of (A) CFU-GM, (B) CFU-F, and (C) LTC-IC killed by the various exposures are shown.