Effects of PEG-rHuMGDF and of SCF, IL-3, and IL-6 on MK growth (A), proplatelet formation (B), and platelet production (C). Marrow (n = 3, ▧) or blood (n = 6, ▩) CD34⁺cells were grown from 11 to 14 days in serum-free conditions, in the presence of PEG-rHuMGDF (10 ng/mL), IL-3 (100 U/mL), and different combinations of these two different cytokines with SCF (50 ng/mL) and IL-6 (100 U/mL). Asterisks denote a significative difference (P < .05) in comparison with culture with 1 ng/mL PEG-rHuMGDF alone.