In vitro colony formation of erythroid progenitors from mice of the indicated genotypes.

Numbers refer to scored colonies/10⁵ nucleated bone marrow cells from the femurs (A,C,D) or spleens (B) of 10- to 12-week-old female mice. Results are based on 3 sets of independent experiments per study. (A) CFU-E frequencies, for either WT (black) or EpoR^+/−(white) bone marrow cells, grown in the indicated concentration of rhEPO. * and ** denote P < .05 and < .005, respectively, when each value is compared with the same genotype value with 1.0 U/mL EPO. In comparing WT withEpoR^+/−, P < .002 at each EPO concentration. (B) CFU-E frequencies, spleen. Statistical analysis was performed and indicated as in part A. (C) BFU-E frequencies, bone marrow. (D) CFU-E frequencies, bone marrow. Compared with WT values at the same EPO concentration, * and ** denote P < .05 and < .005, respectively. % and @ represent P < .05 when comparing WT mice with mice lacking GM-CSF or IL-3, respectively.