Differentiation of WEHI-3B D⁺ cells expressing LIFR mutants. Cells expressing various chimeric receptors were treated for 4 days with 10 ng/mL of hGM-CSF or 100 ng/mL of IL-6. The NBT-reducing activity of the cells was determined by the colorimetric assay. The data for representative clones are presented as percentages of the values for untreated control cultures. The values represent the averages of duplicate assays ± standard error.