Dose-dependent suppression of CFU-Meg, CFU-GM, and BFU-E colony formation by TGF-β1. CD34⁺ cells for colony assays were obtained from 3 different normal volunteers (cases no. 1, 2, and 3). CFU-Meg colony assay from 1 × 10³ of CD34⁺ cells was performed with TPO at a concentration of 100 ng/mL (○), 10 ng/mL (•), or 1.0 ng/mL (▪) in the presence of 0.1 and 1.0 ng/mL of TGF-β1. CFU-GM and BFU-E colony assay was performed with 100 ng/mL of G-CSF and 2 U/mL of EPO, respectively, in the presence of TGF-β1 (0.1 or 1.0 ng/mL). Data are shown as the mean of triplicate colony number with error bars as SD.