Concentration dependency of TGF-β₁–mediated inhibition of Fas-induced growth suppression of Lin⁻ BM cells. Two thousand Lin⁻ BM cells were plated in IMDM supplemented with 20% FCS and 1.2% methylcellulose as described in Materials and Methods. All cultures were supplemented with GM-CSF 20 ng/mL and TNF-α 20 ng/mL, in the absence (▤) or presence (▪) of 0.5 μg/mL Jo2, from initiation of culture. As indicated, TGF-β₁ was added at increasing concentrations. Cultures were scored for colony formation (<50 cells) after 7 to 9 days of incubation. An irrelevant hamster control IgG antibody had no effect on colony formation. Results represent the mean values from four separate experiments with duplicate determinations; error bars show the SEM.