Optimization of NK cell expansion. CD3^dep PBMCs were cultured as described in and the percentages of CD56⁺/CD16⁺ double-positive NK cells. (A) and CD3⁺ T cells. (B) were determined. The number of CD56⁺/CD16⁺ double-positive NK cells was counted using flow cytometry. (C) The data from three independent experiments performed in triplicate are expressed as mean±SD.