Echinomycin treatment does not affect long-term HSC activity as revealed by competitive BMT. Three groups of CD45.1⁺ mice prepared in an identical fashion to those described in the legend of Fig. 2 were killed on day 165. Their BM cells were mixed with recipient wild-type CD45.2⁺ BM cells in a 1:1 ratio and transplanted into the lethally irradiated CD45.2⁺ host. Twenty-nine weeks later, the recipient mice were killed to assess the hematopoiesis of the CD45.1⁺ HSCs. (A) Long-term hematopoiesis based on frequency of CD45.1⁺ cells. (B) Frequency of B and T cells among CD45.1⁺ BM cells. (C) Frequency of granulocytes among CD45.1⁺ BM cells. (D) Summary data of A-C. Data shown represent the means ± SD for 5 mice. These data have been reproduced in 2 independent experiments.