Flow cytometric analysis of cell surface markers of NK and myeloid cell differentiation. UCB CD34⁺ cells were purified and cultured in the presence of SCF, Flt3-L, IL-7, IL-15, and IL-21 (cytokine-mix medium). After 12 days (A) and 20 days (B) of culture cells were analyzed for the expression of the indicated markers. NK activating and inhibitory receptors expression was analyzed gating on CD161⁺CD56⁺ cells. Black line with empty profile in histograms indicates isotype control.