Effect of cytokines on the production of polyploid MK by CD34⁺CD41⁺ MK progenitors. CD34⁺CD41⁺ BM cells were cultured for 7 days with various combinations of growth factors, enumerated, washed, and stained with anti-CD41 and PI. The proportion of the cells with DNA content greater than 8N was determined. The results shown are the mean ± SD of three to five independent experiments. NA, not available.