CD56 expression to determine the kinetics of generation of NK cells from Lin⁻ cells in cultures with IL-2 and IL-15.

Lin⁻ cells (2 × 10⁵/well) were cultured with Sl/Sl⁴hSCF²²⁰ cells and rIL-2 (50 U/mL), rIL-15 (10 ng/mL), or their combination, as described in “Materials and methods.” At the indicated times, the number of NK cells was calculated as the product of the number of viable cells recovered by the percentage of CD3⁻/CD56⁺ cells in 2-color immunofluorescence. Points are mean values from 3 to 20 experiments performed for each time and condition. In 26- to 34-day culture: IL-2 and IL-15 versus IL-2 or IL-15 alone, P < .05.