Analysis of NF-κB p65 nuclear localization in human CD34+ cells from various sources by confocal microscopy. Hematopoietic progenitors isolated from BM (A), CB (B), and MPB (C) were incubated or not (basal) with neutralizing anti—IL-15 or anti—IL-15Rα mAbs for 1 hour and were analyzed by confocal microscopy (original magnification, × 63), for NF-κB p65 expression and nuclear localization. MPB progenitors were also stimulated with TNF-α for 15 minutes. Cells were permeabilized and labeled with anti—NF-κB p65 antibodies, followed by incubation with Alexa Fluor488-GARa antibody. Propidium iodide stained the nuclei in red, and NF-κB p65 stained in green. As negative controls, cells were incubated with only the second reagent and propidium iodide. These data are representative of 3 different experiments.