Different effects of IL-6/sIL-6R on the generation of Mks from CD34⁺ IL-6R⁻ and CD34⁺IL-6R⁺ cells. (A) Selection of CD34⁺IL-6R⁻ and CD34⁺ IL-6R⁺ cells from human umbilical cord blood MNCs by flow cytometry. R2: CD34⁺ IL-6R⁺, R3: CD34⁺IL-6R⁻ cells. (B) Megakaryocyte generation from the two populations of the CD34⁺ cells. 2,000 CD34⁺IL-6R⁻ cells and CD34⁺ IL-6R⁺cells sorted by FACS were initiated in serum-free culture, respectively. The total number of Mks generated by each combination was determined at day 10. Results are from one representative experiment. Similar results were obtained in three additional experiments.