Clonogenic potential ability of (A) hIL-3 R,β_c cells and (B) hGM R,β_c cells. (A) hIL-3 R,β_c cells and (B) hGM R,β_ccells were cultured in the presence of the cognate cytokine (0.1 to 10 ng/mL) alone or in combination with cytokines that promote granulocyte/macrophage development (G Diff) for 7 days before washing free of growth factors and plating (at a cell density of 2,000 cells/plate) in triplicate into soft agar containing 5% (vol/vol) mIL-3. Cells cultured in recombinant (r) mIL-3 (10 ng/mL) for 7 days before plating were used as the positive control. Data are from a single representative experiment of 3 and the values shown are the mean of triplicates ± SD. Similar results were obtained with at least 3 clones of each transfect.