Growth factor responsiveness of EBHX cell lines. EBHX cells were cultured in methylcellulose in the presence of the indicated cytokines and the developing colonies scored 7 to 8 days later. EBHX1 cells were cultured at 1 × 10⁴ to 5 × 10⁴cells/mL, EBHX11 at 250 to 750 cells/mL, and EBHX 14 at 1 × 10⁴ to 5 × 10⁴ cells/mL. Maximum response was determined by the number of colonies that grew in response to a broad mixture of cytokines, which included IL-3, IL-6, IL-11, Epo, KL, LIF, GM-CSF, G-CSF, and M-CSF. Colony-forming cell frequencies in this mixture were approximately 14% for EBHX1, 50% for EBHX11, and 20% for EBHX14. Cytokines were used at the following concentrations: IL-2, 1% conditioned medium; IL-3, 1 ng/mL; IL-6, 5 ng/mL; IL-7, 16 ng/mL; IL-11, 25 ng/mL; Epo, 2 U/mL; KL, 100 ng/mL; LIF, 1 ng/mL; IL-4, 1% conditioned medium; TPO, 5 ng/mL; G-CSF, 30 ng/mL; GM-CSF, 15 ng/mL; M-CSF, 5 ng/mL; IGF-1, 5 ng/mL; and basic FGF, 10 ng/mL. Bars represent standard error of the mean (SEM) from three independent experiments.