KIR expression and functional analysis of NK cells developed on human MSCs and murine stromal feeder cells. CD34⁺ HSPCs were isolated from CB and seeded onto human MSCs and 3 murine stromal feeder cells (EL08.1D2, OP9, and OP9-DL1). (A) Representative flow cytometric analysis of KIR2DL3 expression on NK cells on day 25. (B) Frequency of KIR2DL3 expression (data are mean and standard deviation of 3 independent experiments). (C) Comparison of granzyme B and perforin expression in NK cells developed on EL08.1D2 or MSCs by intracytoplasmic staining and flow cytometry. (D) Cytotoxicity of NK cells cultured on EL08.1D2 or MSCs against K562 target cells at an effector/target ratio of 5:1. *P < .05, Fisher t test.