Effects of the soluble receptor on the cell cycle. CD34⁺ cells from 2 PMF patients (m1 and m3) were cultured without growth factor in the absence (A and G) or the presence of the sMpl-Fc (B and H), with 10 ng/mL PEG-rhuMGDF in the absence (C and I) or the presence of the sMpl-Fc (D and J) or with a combination of 3 cytokines (IL-3, IL-6, and SCF) in the absence (E and K) or the presence of 5 μg/mL sMpl-Fc (F and L). Cell cycle was studied after staining with propidium iodide after 4 days of culture. Two other patients were studied, and similar results were obtained.